Cleidocranial dysplasia (CCD) spectrum disorder is a skeletal dysplasia that represents a clinical continuum ranging from classic CCD (triad of delayed closure of the cranial sutures, hypoplastic or aplastic clavicles, and dental abnormalities) to mild CCD to isolated dental anomalies without the skeletal features. Most individuals come to diagnosis because they have classic features. At birth, affected individuals typically have abnormally large, wide-open fontanelles that may remain open throughout life. Clavicular hypoplasia can result in narrow, sloping shoulders that can be opposed at the midline. Moderate short stature may be observed, with most affected individuals being shorter than their unaffected sibs. Dental anomalies may include supernumerary teeth, eruption failure of the permanent teeth, and presence of the second permanent molar with the primary dentition. Individuals with CCD spectrum disorder are at increased risk of developing recurrent sinus infections, recurrent ear infections leading to conductive hearing loss, and upper-airway obstruction. Intelligence is typically normal.

Individuals with 22q11.2 deletion syndrome (22q11.2DS) can present with a wide range of features that are highly variable, even within families. The major clinical manifestations of 22q11.2DS include congenital heart disease, particularly conotruncal malformations (ventricular septal defect, tetralogy of Fallot, interrupted aortic arch, and truncus arteriosus), palatal abnormalities (velopharyngeal incompetence, submucosal cleft palate, bifid uvula, and cleft palate), immune deficiency, characteristic facial features, and learning difficulties. Hearing loss can be sensorineural and/or conductive. Laryngotracheoesophageal, gastrointestinal, ophthalmologic, central nervous system, skeletal, and genitourinary anomalies also occur. Psychiatric illness and autoimmune disorders are more common in individuals with 22q11.2DS.

Hallermann-Streiff syndrome is characterized by a typical skull shape (brachycephaly with frontal bossing), hypotrichosis, microphthalmia, cataracts, beaked nose, micrognathia, skin atrophy, dental anomalies, and proportionate short stature (Hallermann, 1948; Streiff, 1950; Francois, 1958). Mental retardation is present in a minority of cases (Gorlin et al., 1990).

Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by contiguous gene deletion of TRPS1, RAD21, and EXT1). Both types of TRPS are characterized by distinctive facial features; ectodermal features (fine, sparse, depigmented, and slow growing hair; dystrophic nails; and small breasts); and skeletal findings (short stature; short feet; brachydactyly with ulnar or radial deviation of the fingers; and early, marked hip dysplasia). TRPS II is characterized by multiple osteochondromas (typically first observed clinically on the scapulae and around the elbows and knees between ages 1 month and 6 years) and an increased risk of mild-to-moderate intellectual disability.

FBN1-related Marfan syndrome (Marfan syndrome), a systemic disorder of connective tissue with a high degree of clinical variability, comprises a broad phenotypic continuum ranging from mild (features of Marfan syndrome in one or a few systems) to severe and rapidly progressive neonatal multiorgan disease. Cardinal manifestations involve the ocular, skeletal, and cardiovascular systems. Ocular findings include myopia (>50% of affected individuals); ectopia lentis (seen in approximately 60% of affected individuals); and an increased risk for retinal detachment, glaucoma, and early cataracts. Skeletal system manifestations include bone overgrowth and joint laxity; disproportionately long extremities for the size of the trunk (dolichostenomelia); overgrowth of the ribs that can push the sternum in (pectus excavatum) or out (pectus carinatum); and scoliosis that ranges from mild to severe and progressive. The major morbidity and early mortality in Marfan syndrome relate to the cardiovascular system and include dilatation of the aorta at the level of the sinuses of Valsalva (predisposing to aortic tear and rupture), mitral valve prolapse with or without regurgitation, tricuspid valve prolapse, and enlargement of the proximal pulmonary artery. Severe and prolonged regurgitation of the mitral and/or aortic valve can predispose to left ventricular dysfunction and occasionally heart failure. With proper management, the life expectancy of someone with Marfan syndrome approximates that of the general population.

The X-linked otopalatodigital (X-OPD) spectrum disorders, characterized primarily by skeletal dysplasia, include the following: Otopalatodigital syndrome type 1 (OPD1). Otopalatodigital syndrome type 2 (OPD2). Frontometaphyseal dysplasia type 1 (FMD1). Melnick-Needles syndrome (MNS). Terminal osseous dysplasia with pigmentary skin defects (TODPD). In OPD1, most manifestations are present at birth; females can present with severity similar to affected males, although some have only mild manifestations. In OPD2, females are less severely affected than related affected males. Most males with OPD2 die during the first year of life, usually from thoracic hypoplasia resulting in pulmonary insufficiency. Males who live beyond the first year of life are usually developmentally delayed and require respiratory support and assistance with feeding. In FMD1, females are less severely affected than related affected males. Males do not experience a progressive skeletal dysplasia but may have joint contractures and hand and foot malformations. Progressive scoliosis is observed in both affected males and females. In MNS, wide phenotypic variability is observed; some individuals are diagnosed in adulthood, while others require respiratory support and have reduced longevity. MNS in males results in perinatal lethality in all recorded cases. TODPD, seen only in females, is characterized by a skeletal dysplasia that is most prominent in the digits, pigmentary defects of the skin, and recurrent digital fibromata.

Orofaciodigital syndrome II (OFD2), also known as Mohr syndrome, is characterized by cleft lip/palate, lobulated tongue with nodules, dental anomalies including tooth agenesis, maxillary hypoplasia, conductive hearing loss, and poly-, syn-, and brachydactyly. Mesomelic shortening of the limbs has also been observed (Mohr, 1941; Gorlin, 1982; Monroe et al., 2016).

Pierre Robin sequence is a craniofacial anomaly comprising mandibular hypoplasia, cleft secondary palate, and glossoptosis leading to life-threatening obstructive apnea and feeding difficulties during the neonatal period (summary by Tan et al., 2013).

Hutchinson-Gilford progeria syndrome (HGPS) is characterized by clinical features that typically develop in childhood and resemble some features of accelerated aging. Children with HGPS usually appear normal at birth. Profound failure to thrive occurs during the first year. Characteristic facial features include head that is disproportionately large for the face, narrow nasal ridge, narrow nasal tip, thin vermilion of the upper and lower lips, small mouth, and retro- and micrognathia. Common features include loss of subcutaneous fat, delayed eruption and loss of primary teeth, abnormal skin with small outpouchings over the abdomen and upper thighs, alopecia, nail dystrophy, coxa valga, and progressive joint contractures. Later findings include low-frequency conductive hearing loss, dental crowding, and partial lack of secondary tooth eruption. Motor and mental development is normal. Death occurs as a result of complications of severe atherosclerosis, either cardiac disease (myocardial infarction or heart failure) or cerebrovascular disease (stroke), generally between ages six and 20 years. Average life span is approximately 14.5 years.

Mucopolysaccharidosis type I (MPS I) is a progressive multisystem disorder with features ranging over a continuum of severity. While affected individuals have traditionally been classified as having one of three MPS I syndromes (Hurler syndrome, Hurler-Scheie syndrome, or Scheie syndrome), no easily measurable biochemical differences have been identified and the clinical findings overlap. Affected individuals are best described as having either a phenotype consistent with either severe (Hurler syndrome) or attenuated MPS I, a distinction that influences therapeutic options. Severe MPS I. Infants appear normal at birth. Typical early manifestations are nonspecific (e.g., umbilical or inguinal hernia, frequent upper respiratory tract infections before age 1 year). Coarsening of the facial features may not become apparent until after age one year. Gibbus deformity of the lower spine is common and often noted within the first year. Progressive skeletal dysplasia (dysostosis multiplex) involving all bones is universal, as is progressive arthropathy involving most joints. By age three years, linear growth decreases. Intellectual disability is progressive and profound but may not be readily apparent in the first year of life. Progressive cardiorespiratory involvement, hearing loss, and corneal clouding are common. Without treatment, death (typically from cardiorespiratory failure) usually occurs within the first ten years of life. Attenuated MPS I. Clinical onset is usually between ages three and ten years. The severity and rate of disease progression range from serious life-threatening complications leading to death in the second to third decade, to a normal life span complicated by significant disability from progressive joint manifestations and cardiorespiratory disease. While some individuals have no neurologic involvement and psychomotor development may be normal in early childhood, learning disabilities and psychiatric manifestations can be present later in life. Hearing loss, cardiac valvular disease, respiratory involvement, and corneal clouding are common.

Dubowitz syndrome (DS) is a rare multiple congenital syndrome characterized primarly by growth retardation, microcephaly, distinctive facial dysmorphism, cutaneous eczema, a mild to severe intellectual deficit and genital abnormalities.

Smith-Lemli-Opitz syndrome (SLOS) is a congenital multiple-anomaly / cognitive impairment syndrome caused by an abnormality in cholesterol metabolism resulting from deficiency of the enzyme 7-dehydrocholesterol (7-DHC) reductase. It is characterized by prenatal and postnatal growth restriction, microcephaly, moderate-to-severe intellectual disability, and multiple major and minor malformations. The malformations include distinctive facial features, cleft palate, cardiac defects, underdeveloped external genitalia in males, postaxial polydactyly, and 2-3 syndactyly of the toes. The clinical spectrum is wide; individuals with normal development and only minor malformations have been described.

Aarskog-Scott syndrome is a genetic disorder that affects the development of many parts of the body, most commonly the head and face, the hands and feet, and the genitals and urinary system (genitourinary tract). This condition mainly affects males, although females may have mild features of the syndrome.\n\nPeople with Aarskog-Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Affected individuals can also have wide, flat feet with broad, rounded toes. Other abnormalities in people with Aarskog-Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).\n\nMost males with Aarskog-Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia).\n\nThe intellectual development of people with Aarskog-Scott syndrome varies widely. Most individuals with Aarskog-Scott syndrome have normal intelligence; however, some may have mild learning and behavior problems, and in rare cases, severe intellectual disability has been reported.

Thrombocytopenia absent radius (TAR) syndrome is characterized by bilateral absence of the radii with the presence of both thumbs, and thrombocytopenia that is generally transient. Thrombocytopenia may be congenital or may develop within the first few weeks to months of life; in general, thrombocytopenic episodes decrease with age. Cow's milk allergy is common and can be associated with exacerbation of thrombocytopenia. Other anomalies of the skeleton (upper and lower limbs, ribs, and vertebrae), heart, and genitourinary system (renal anomalies and agenesis of uterus, cervix, and upper part of the vagina) can occur.

DA3, or Gordon syndrome, is distinguished from other distal arthrogryposes by short stature and cleft palate (summary by Bamshad et al., 2009). There are 2 syndromes with features overlapping those of DA3 that are also caused by heterozygous mutation in PIEZO2: distal arthrogryposis type 5 (DA5; 108145) and Marden-Walker syndrome (MWKS; 248700), which are distinguished by the presence of ocular abnormalities and mental retardation, respectively. McMillin et al. (2014) suggested that the 3 disorders may represent variable expressivity of the same condition. For a phenotypic description and a discussion of genetic heterogeneity of distal arthrogryposis, see DA1 (108120).

Congenital contractural arachnodactyly (CCA) appears to comprise a broad phenotypic spectrum. Classic CCA is characterized by arachnodactyly; flexion contractures of multiple joints including elbows, knees, hips, ankles, and/or fingers; kyphoscoliosis (usually progressive); a marfanoid habitus (a long and slender build, dolichostenomelia, pectus deformity, muscular hypoplasia, highly arched palate); and abnormal "crumpled" ears. At the mildest end, parents who are diagnosed retrospectively upon evaluation of their more severely affected child may show a lean body build, mild arachnodactyly, mild contractures without impairment, and minor ear abnormalities. At the most severe end is "severe CCA with cardiovascular and/or gastrointestinal anomalies," a rare phenotype in infants with pronounced features of CCA (severe crumpling of the ears, arachnodactyly, contractures, congenital scoliosis, and/or hypotonia) and severe cardiovascular and/or gastrointestinal anomalies. Phenotypic expression can vary within and between families.

An autosomal recessive subtype of cerebrooculofacioskeletal syndrome caused by mutation(s) in the ERCC6 gene, encoding DNA excision repair protein ERCC-6.

A very rare syndrome with characteristics of the combination of hypertelorism, cleft lip and palate and microtia. Nine cases have been reported in the literature in seven families. Some patients have associated cardiac or renal congenital malformations. Short stature and intellectual deficiency are common. The reported cases support autosomal recessive inheritance.

The most basic description of Moebius syndrome is a congenital facial palsy with impairment of ocular abduction. The facial nerve (cranial nerve VII) and abducens nerve (CN VI) are most frequently involved, but other cranial nerves may be involved as well. Other variable features include orofacial dysmorphism and limb malformations. Mental retardation has been reported in a subset of patients. Most cases of Moebius syndrome are sporadic, but familial occurrence has been reported (Verzijl et al., 2003). The definition of and diagnostic criteria for Moebius syndrome have been controversial and problematic. The syndrome has most frequently been confused with hereditary congenital facial paresis (HCFP; see 601471), which is restricted to involvement of the facial nerve and no other abnormalities. Verzijl et al. (2003) and Verzijl et al. (2005) concluded that HCFP and Moebius syndrome are distinct disorders, and that Moebius syndrome is a complex developmental disorder of the brainstem. Moebius syndrome was defined at the Moebius Syndrome Foundation Research Conference in 2007 as congenital, nonprogressive facial weakness with limited abduction of one or both eyes. Additional features can include hearing loss and other cranial nerve dysfunction, as well as motor, orofacial, musculoskeletal, neurodevelopmental, and social problems (summary by Webb et al., 2012). Kumar (1990) provided a review of Moebius syndrome, which was critiqued by Lipson et al. (1990). Briegel (2006) provided a review of Moebius sequence with special emphasis on neuropsychiatric findings.

Pycnodysostosis is characterized by short-limbed short stature, typical facial appearance (convex nasal ridge and small jaw with obtuse mandibular angle), osteosclerosis with increased bone fragility, acroosteolysis of the distal phalanges, delayed closure of the cranial sutures, and dysplasia of the clavicle. In affected individuals, the facial features become more prominent with age, likely due to progressive acroosteolysis of the facial bones, but can usually be appreciated from early childhood, particularly the small jaw and convex nasal ridge. Additional features include dental and nail anomalies. Intelligence is typically normal with mild psychomotor difficulties reported in some individuals.

Treacher Collins syndrome (TCS) is characterized by bilateral and symmetric downslanting palpebral fissures, malar hypoplasia, micrognathia, and external ear abnormalities. Hypoplasia of the zygomatic bones and mandible can cause significant feeding and respiratory difficulties. About 40%-50% of individuals have conductive hearing loss attributed most commonly to malformation of the ossicles and hypoplasia of the middle ear cavities. Inner ear structures tend to be normal. Other, less common abnormalities include cleft palate and unilateral or bilateral choanal stenosis or atresia. Typically intellect is normal.

PAFAH1B1-related lissencephaly/subcortical band heterotopia (SBH) comprises a spectrum of severity. Affected newborns typically have mild-to-moderate hypotonia, feeding difficulties, and poor head control. During the first years, neurologic examination typically demonstrates poor visual tracking and response to sounds, axial hypotonia, and mild distal spasticity that can transition over time to more severe spasticity. Seizures occur in more than 90% of individuals with lissencephaly and often include infantile spasms. Seizures are often drug resistant, but even with good seizure control, the best developmental level achieved (excluding the few individuals with partial lissencephaly) is the equivalent of about age three to five months. In individuals with PAFAH1B1-related lissencephaly/SBH, developmental delay ranges from mild to severe. Other findings in PAFAH1B1-related lissencephaly/SBH include feeding issues and aspiration (which may result in need for gastrostomy tube placement), progressive microcephaly, and occasional developmental regression.

Cohen syndrome is characterized by failure to thrive in infancy and childhood; truncal obesity in the teen years; early-onset hypotonia and developmental delays; microcephaly developing during the first year of life; moderate to profound psychomotor retardation; progressive retinochoroidal dystrophy and high myopia; neutropenia in many with recurrent infections and aphthous ulcers in some; a cheerful disposition; joint hypermobility; and characteristic facial features.

Freeman-Sheldon syndrome (FSS), or DA2A, is phenotypically similar to DA1. In addition to contractures of the hands and feet, FSS is characterized by oropharyngeal abnormalities, scoliosis, and a distinctive face that includes a very small oral orifice (often only a few millimeters in diameter at birth), puckered lips, and an H-shaped dimple of the chin; hence, FSS has been called 'whistling face syndrome.' The limb phenotypes of DA1 and FSS may be so similar that they can only be distinguished by the differences in facial morphology (summary by Bamshad et al., 2009). For a general phenotypic description and a discussion of genetic heterogeneity of distal arthrogryposis, see DA1 (108120).

The trismus-pseudocamptodactyly syndrome is a distal arthrogryposis characterized by an inability to open the mouth fully (trismus) and pseudocamptodactyly in which wrist dorsiflexion, but not volar flexion, produces involuntary flexion contracture of distal and proximal interphalangeal joints. In these patients, trismus complicates dental care, feeding during infancy, and intubation for anesthesia, and the pseudocamptodactyly impairs manual dexterity, with consequent occupational and social disability (summary by Veugelers et al., 2004).

Marshall syndrome (MRSHS) is characterized by midfacial hypoplasia, cleft palate, ocular anomalies including high myopia and cataracts, sensorineural hearing loss, short stature with spondyloepiphyseal dysplasia, and arthropathy. In contrast to Stickler syndrome type II, it has less severe eye findings but striking ocular hypertelorism, more pronounced maxillary hypoplasia, and ectodermal abnormalities (summary by Shanske et al., 1997 and Ala-Kokko and Shanske, 2009).

Agnathia-otocephaly (AGOTC) is a rare condition characterized by mandibular hypoplasia or agnathia, ventromedial auricular malposition (melotia) and/or auricular fusion (synotia), and microstomia with oroglossal hypoplasia or aglossia. Holoprosencephaly is the most commonly identified association, but skeletal, genitourinary, and cardiovascular anomalies, and situs inversus have been reported. The disorder is almost always lethal (review by Faye-Petersen et al., 2006).

Nager syndrome is the prototype for a group of disorders collectively referred to as the acrofacial dysostoses (AFDs), which are characterized by malformation of the craniofacial skeleton and the limbs. The major facial features of Nager syndrome include downslanted palpebral fissures, midface retrusion, and micrognathia, the latter of which often requires the placement of a tracheostomy in early childhood. Limb defects typically involve the anterior (radial) elements of the upper limbs and manifest as small or absent thumbs, triphalangeal thumbs, radial hypoplasia or aplasia, and radioulnar synostosis. Phocomelia of the upper limbs and, occasionally, lower-limb defects have also been reported. The presence of anterior upper-limb defects and the typical lack of lower-limb involvement distinguishes Nager syndrome from Miller syndrome (263750), another rare AFD; however, distinguishing Nager syndrome from other AFDs, including Miller syndrome, can be challenging (summary by Bernier et al., 2012).

Miller syndrome, also known as postaxial acrofacial dysostosis (POADS), is a rare autosomal recessive disorder characterized clinically by severe micrognathia, cleft lip and/or palate, hypoplasia or aplasia of the postaxial elements of the limbs, coloboma of the eyelids, and supernumerary nipples (summary by Ng et al., 2010).

Multiple pterygium syndromes comprise a group of multiple congenital anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures (arthrogryposis) (Morgan et al., 2006). The multiple pterygium syndromes are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal (253290) and nonlethal (Escobar) types.

Femoral-facial syndrome (FFS), also known as femoral hypoplasia-unusual facies syndrome (FHUFS), is a rare and sporadic multiple congenital anomaly syndrome comprising bilateral femoral hypoplasia and characteristic facial features, such as long philtrum, thin upper lip, micrognathia with or without cleft palate, upward-slanting palpebral fissures, and a short nose with broad tip. Other features, such as renal anomalies, are more variable (summary by Nowaczyk et al., 2010).

Holt-Oram syndrome (HOS) is characterized by upper-limb defects, congenital heart malformation, and cardiac conduction disease. Upper-limb malformations may be unilateral, bilateral/symmetric, or bilateral/asymmetric and can range from triphalangeal or absent thumb(s) to phocomelia. Other upper-limb malformations can include unequal arm length caused by aplasia or hypoplasia of the radius, fusion or anomalous development of the carpal and thenar bones, abnormal forearm pronation and supination, abnormal opposition of the thumb, sloping shoulders, and restriction of shoulder joint movement. An abnormal carpal bone is present in all affected individuals and may be the only evidence of disease. A congenital heart malformation is present in 75% of individuals with HOS and most commonly involves the septum. Atrial septal defect and ventricular septal defect can vary in number, size, and location. Complex congenital heart malformations can also occur in individuals with HOS. Individuals with HOS with or without a congenital heart malformation are at risk for cardiac conduction disease. While individuals may present at birth with sinus bradycardia and first-degree atrioventricular (AV) block, AV block can progress unpredictably to a higher grade including complete heart block with and without atrial fibrillation.

The NSDHL-related disorders include: CHILD (congenital hemidysplasia with ichthyosiform nevus and limb defects) syndrome, an X-linked condition that is usually male lethal during gestation and thus predominantly affects females; and CK syndrome, an X-linked disorder that affects males. CHILD syndrome is characterized by unilateral distribution of ichthyosiform (yellow scaly) skin lesions and ipsilateral limb defects that range from shortening of the metacarpals and phalanges to absence of the entire limb. Intellect is usually normal. The ichthyosiform skin lesions are usually present at birth or in the first weeks of life; new lesions can develop in later life. Nail changes are also common. The heart, lung, and kidneys can also be involved. CK syndrome (named for the initials of the original proband) is characterized by mild to severe cognitive impairment and behavior problems (aggression, attention deficit hyperactivity disorder, and irritability). All affected males reported have developed seizures in infancy and have cerebral cortical malformations and microcephaly. All have distinctive facial features, a thin habitus, and relatively long, thin fingers and toes. Some have scoliosis and kyphosis. Strabismus is common. Optic atrophy is also reported.

The FLNB disorders include a spectrum of phenotypes ranging from mild to severe. At the mild end are spondylocarpotarsal synostosis (SCT) syndrome and Larsen syndrome; at the severe end are the phenotypic continuum of atelosteogenesis types I (AOI) and III (AOIII) and Piepkorn osteochondrodysplasia (POCD). SCT syndrome is characterized by postnatal disproportionate short stature, scoliosis and lordosis, clubfeet, hearing loss, dental enamel hypoplasia, carpal and tarsal synostosis, and vertebral fusions. Larsen syndrome is characterized by congenital dislocations of the hip, knee, and elbow; clubfeet (equinovarus or equinovalgus foot deformities); scoliosis and cervical kyphosis, which can be associated with a cervical myelopathy; short, broad, spatulate distal phalanges; distinctive craniofacies (prominent forehead, depressed nasal bridge, malar flattening, and widely spaced eyes); vertebral anomalies; and supernumerary carpal and tarsal bone ossification centers. Individuals with SCT syndrome and Larsen syndrome can have midline cleft palate and hearing loss. AOI and AOIII are characterized by severe short-limbed dwarfism; dislocated hips, knees, and elbows; and clubfeet. AOI is lethal in the perinatal period. In individuals with AOIII, survival beyond the neonatal period is possible with intensive and invasive respiratory support. Piepkorn osteochondrodysplasia (POCD) is a perinatal-lethal micromelic dwarfism characterized by flipper-like limbs (polysyndactyly with complete syndactyly of all fingers and toes, hypoplastic or absent first digits, and duplicated intermediate and distal phalanges), macrobrachycephaly, prominant forehead, hypertelorism, and exophthalmos. Occasional features include cleft palate, omphalocele, and cardiac and genitourinary anomalies. The radiographic features at mid-gestation are characteristic.

The Murk Jansen type of metaphyseal chondrodysplasia is characterized by severe short stature, short bowed limbs, clinodactyly, prominent upper face, and small mandible. Hypercalcemia and hypophosphatemia occur despite the lack of parathyroid abnormalities (summary by Cohen, 2002).

Baller-Gerold syndrome (BGS) can be suspected at birth in an infant with craniosynostosis and upper limb abnormality. The coronal suture is most commonly affected; the metopic, lambdoid, and sagittal sutures may also be involved alone or in combination. Upper limb abnormality can include a combination of thumb hypo- or aplasia and radial hypo- or aplasia and may be asymmetric. Malformation or absence of carpal or metacarpal bones has also been described. Skin lesions may appear anytime within the first few years after birth, typically beginning with erythema of the face and extremities and evolving into poikiloderma. Slow growth is apparent in infancy with eventual height and length typically at 4 SD below the mean.

Cerebrocostomandibular syndrome (CCMS) is a rare autosomal dominant disorder characterized by branchial arch-derivative and thoracic malformations. A key craniofacial characteristic is micrognathia, often associated with cleft palate and feeding and airway difficulties. Patients with CCMS have a narrow chest and striking posterior rib gaps which distinguish this condition (summary by Tooley et al., 2016). See CDG2G (611209) for a cerebrocostomandibular-like syndrome.

Lymphedema-distichiasis syndrome (referred to as LDS in this GeneReview) is characterized by lower-limb lymphedema, and distichiasis (aberrant eyelashes ranging from a full set of extra eyelashes to a single hair). Lymphedema typically appears in late childhood or puberty, is confined to the lower limbs with or without involvement of the external genitalia, and is often asymmetric; severity varies within families. Males develop edema at an earlier age and have more problems with cellulitis than females. Distichiasis, which may be present at birth, is observed in 94% of affected individuals. About 75% of affected individuals have ocular findings including corneal irritation, recurrent conjunctivitis, and photophobia; other common findings include varicose veins and ptosis.

CHD7 disorder encompasses the entire phenotypic spectrum of heterozygous CHD7 pathogenic variants that includes CHARGE syndrome as well as subsets of features that comprise the CHARGE syndrome phenotype. The mnemonic CHARGE syndrome, introduced in the premolecular era, stands for coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies (including deafness). Following the identification of the genetic cause of CHD7 disorder, the phenotypic spectrum expanded to include cranial nerve anomalies, vestibular defects, cleft lip and/or palate, hypothyroidism, tracheoesophageal anomalies, brain anomalies, seizures, and renal anomalies. Life expectancy highly depends on the severity of manifestations; mortality can be high in the first few years when severe birth defects (particularly complex heart defects) are present and often complicated by airway and feeding issues. In childhood, adolescence, and adulthood, decreased life expectancy is likely related to a combination of residual heart defects, infections, aspiration or choking, respiratory issues including obstructive and central apnea, and possibly seizures. Despite these complications, the life expectancy for many individuals can be normal.

Pallister-Killian syndrome (PKS) is a dysmorphic condition involving most organ systems, but is also characterized by a tissue-limited mosaicism; most fibroblasts have 47 chromosomes with an extra small metacentric chromosome, whereas the karyotype of lymphocytes is normal. The extra metacentric chromosome is an isochromosome for part of the short arm of chromosome 12: i(12)(p10) (Peltomaki et al., 1987; Warburton et al., 1987).

Cat eye syndrome (CES) is characterized clinically by the combination of coloboma of the iris and anal atresia with fistula, downslanting palpebral fissures, preauricular tags and/or pits, frequent occurrence of heart and renal malformations, and normal or near-normal mental development. A small supernumerary chromosome (smaller than chromosome 21) is present, frequently has 2 centromeres, is bisatellited, and represents an inv dup(22)(q11).

COL1A1/2 osteogenesis imperfecta (COL1A1/2-OI) is characterized by fractures with minimal or absent trauma, variable dentinogenesis imperfecta (DI), and, in adult years, hearing loss. The clinical features of COL1A1/2-OI represent a continuum ranging from perinatal lethality to individuals with severe skeletal deformities, mobility impairments, and very short stature to nearly asymptomatic individuals with a mild predisposition to fractures, normal dentition, normal stature, and normal life span. Fractures can occur in any bone but are most common in the extremities. DI is characterized by gray or brown teeth that may appear translucent, wear down, and break easily. COL1A1/2-OI has been classified into four types based on clinical presentation and radiographic findings. This classification system can be helpful in providing information about prognosis and management for a given individual. The four more common OI types are now referred to as follows: Classic non-deforming OI with blue sclerae (previously OI type I). Perinatally lethal OI (previously OI type II). Progressively deforming OI (previously OI type III). Common variable OI with normal sclerae (previously OI type IV).

Prolidase deficiency is characterized by skin lesions (typically severe, chronic, recalcitrant, and painful skin ulcers of the lower extremities and telangiectasias of the face and hands), recurrent infections (particularly of the skin and respiratory tract), dysmorphic facial features, variable intellectual disability, and organomegaly (typically splenomegaly but occasionally associated with hepatomegaly) with elevated liver enzymes. Skeletal anomalies, chronic pulmonary disease, anemia, thrombocytopenia, hypergammaglobulinemia, and hypocomplementemia are observed in a minority of affected individuals. An association between prolidase deficiency and autoimmune conditions – particularly systemic lupus erythematosus (SLE) – has been described.

PLA2G6-associated neurodegeneration (PLAN) comprises a continuum of three phenotypes with overlapping clinical and radiologic features: Infantile neuroaxonal dystrophy (INAD). Atypical neuroaxonal dystrophy (atypical NAD). PLA2G6-related dystonia-parkinsonism. INAD usually begins between ages six months and three years with psychomotor regression or delay, hypotonia, and progressive spastic tetraparesis. Many affected children never learn to walk or lose the ability shortly after attaining it. Strabismus, nystagmus, and optic atrophy are common. Disease progression is rapid, resulting in severe spasticity, progressive cognitive decline, and visual impairment. Many affected children do not survive beyond their first decade. Atypical NAD shows more phenotypic variability than INAD. In general, onset is in early childhood but can be as late as the end of the second decade. The presenting signs may be gait instability, ataxia, or speech delay and autistic features, which are sometimes the only evidence of disease for a year or more. Strabismus, nystagmus, and optic atrophy are common. Neuropsychiatric disturbances including impulsivity, poor attention span, hyperactivity, and emotional lability are also common. The course is fairly stable during early childhood and resembles static encephalopathy but is followed by neurologic deterioration between ages seven and 12 years. PLA2G6-related dystonia-parkinsonism has a variable age of onset, but most individuals present in early adulthood with gait disturbance or neuropsychiatric changes. Affected individuals consistently develop dystonia and parkinsonism (which may be accompanied by rapid cognitive decline) in their late teens to early twenties. Dystonia is most common in the hands and feet but may be more generalized. The most common features of parkinsonism in these individuals are bradykinesia, resting tremor, rigidity, and postural instability.

Pallister-Hall-like syndrome (PHLS) is a pleiotropic autosomal recessive disorder characterized by phenotypic variability. Patients exhibit postaxial polydactyly as well as hypothalamic hamartoma, cardiac and skeletal anomalies, and craniofacial dysmorphisms. Hirschsprung disease has also been observed (Rubino et al., 2018; Le et al., 2020). Pallister-Hall syndrome (146510) is an autosomal dominant disorder with features overlapping those of PHLS, caused by mutation in the GLI3 gene (165240).

D-bifunctional protein deficiency is a disorder of peroxisomal fatty acid beta-oxidation. See also peroxisomal acyl-CoA oxidase deficiency (264470), caused by mutation in the ACOX1 gene (609751) on chromosome 17q25. The clinical manifestations of these 2 deficiencies are similar to those of disorders of peroxisomal assembly, including X-linked adrenoleukodystrophy (ALD; 300100), Zellweger cerebrohepatorenal syndrome (see 214100) and neonatal adrenoleukodystrophy (NALD; see 601539) (Watkins et al., 1995). DBP deficiency has been classified into 3 subtypes depending upon the deficient enzyme activity. Type I is a deficiency of both 2-enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase; type II is a deficiency of hydratase activity alone; and type III is a deficiency of dehydrogenase activity alone. Virtually all patients with types I, II, and III have a severe phenotype characterized by infantile-onset of hypotonia, seizures, and abnormal facial features, and most die before age 2 years. McMillan et al. (2012) proposed a type IV deficiency on the basis of less severe features; these patients have a phenotype reminiscent of Perrault syndrome (PRLTS1; 233400). Pierce et al. (2010) noted that Perrault syndrome and DBP deficiency overlap clinically and suggested that DBP deficiency may be underdiagnosed.

The branchiooculofacial syndrome (BOFS) is characterized by: branchial (cervical or infra- or supra-auricular) skin defects that range from barely perceptible thin skin or hair patch to erythematous "hemangiomatous" lesions to large weeping erosions; ocular anomalies that can include microphthalmia, anophthalmia, coloboma, and nasolacrimal duct stenosis/atresia; and facial anomalies that can include ocular hypertelorism or telecanthus, broad nasal tip, upslanted palpebral fissures, cleft lip or prominent philtral pillars that give the appearance of a repaired cleft lip (formerly called "pseudocleft lip") with or without cleft palate, upper lip pits, and lower facial weakness (asymmetric crying face or partial 7th cranial nerve weakness). Malformed and prominent pinnae and hearing loss from inner ear and/or petrous bone anomalies are common. Intellect is usually normal.

ESCO2 spectrum disorder is characterized by mild-to-severe prenatal growth restriction, limb malformations (which can include bilateral symmetric tetraphocomelia or hypomelia caused by mesomelic shortening), hand anomalies (including oligodactyly, thumb aplasia or hypoplasia, and syndactyly), elbow and knee flexion contractures (involving elbows, wrists, knees, ankles, and feet [talipes equinovarus]), and craniofacial abnormalities (which can include bilateral cleft lip and/or cleft palate, micrognathia, widely spaced eyes, exophthalmos, downslanted palpebral fissures, malar flattening, and underdeveloped ala nasi), ear malformation, and corneal opacities. Intellectual disability (ranging from mild to severe) is common. Early mortality is common among severely affected pregnancies and newborns; mildly affected individuals may survive to adulthood.

Nijmegen breakage syndrome (NBS) is characterized by progressive microcephaly, early growth deficiency that improves with age, recurrent respiratory infections, an increased risk for malignancy (primarily lymphoma), and premature ovarian failure in females. Developmental milestones are attained at the usual time during the first year; however, borderline delays in development and hyperactivity may be observed in early childhood. Intellectual abilities tend to decline over time. Recurrent pneumonia and bronchitis may result in respiratory failure and early death. Other reported malignancies include solid tumors (e.g., medulloblastoma, glioma, rhabdomyosarcoma).

Wiedemann-Rautenstrauch syndrome (WDRTS) is a rare autosomal recessive neonatal progeroid disorder characterized by intrauterine growth retardation, failure to thrive, short stature, a progeroid appearance, hypotonia, and variable mental impairment (summary by Toriello, 1990). Average survival in WDRTS is 7 months, although survival into the third decade of life has been reported (Akawi et al., 2013).

GAPO syndrome is the acronymic designation for a complex of growth retardation, alopecia, pseudoanodontia (failure of tooth eruption), and progressive optic atrophy (Tipton and Gorlin, 1984). Ilker et al. (1999) and Bayram et al. (2014) noted that optic atrophy is not a consistent feature of the disorder.

Oral-facial-digital syndrome is actually a group of related conditions that affect the development of the oral cavity (the mouth and teeth), facial features, and digits (fingers and toes).\n\nResearchers have identified at least 13 potential forms of oral-facial-digital syndrome. The different types are classified by their patterns of signs and symptoms. However, the features of the various types overlap significantly, and some types are not well defined. The classification system for oral-facial-digital syndrome continues to evolve as researchers find more affected individuals and learn more about this disorder.\n\nThe signs and symptoms of oral-facial-digital syndrome vary widely. However, most forms of this disorder involve problems with development of the oral cavity, facial features, and digits. Most forms are also associated with brain abnormalities and some degree of intellectual disability.\n\nAbnormalities of the oral cavity that occur in many types of oral-facial-digital syndrome include a split (cleft) in the tongue, a tongue with an unusual lobed shape, and the growth of noncancerous tumors or nodules on the tongue. Affected individuals may also have extra, missing, or defective teeth. Another common feature is an opening in the roof of the mouth (a cleft palate). Some people with oral-facial-digital syndrome have bands of extra tissue (called hyperplastic frenula) that abnormally attach the lip to the gums.\n\nDistinctive facial features often associated with oral-facial-digital syndrome include a split in the lip (a cleft lip); a wide nose with a broad, flat nasal bridge; and widely spaced eyes (hypertelorism).\n\nAbnormalities of the digits can affect both the fingers and the toes in people with oral-facial-digital syndrome. These abnormalities include fusion of certain fingers or toes (syndactyly), digits that are shorter than usual (brachydactyly), or digits that are unusually curved (clinodactyly). The presence of extra digits (polydactyly) is also seen in most forms of oral-facial-digital syndrome.\n\nOther features occur in only one or a few types of oral-facial digital syndrome. These features help distinguish the different forms of the disorder. For example, the most common form of oral-facial-digital syndrome, type I, is associated with polycystic kidney disease. This kidney disease is characterized by the growth of fluid-filled sacs (cysts) that interfere with the kidneys' ability to filter waste products from the blood. Other forms of oral-facial-digital syndrome are characterized by neurological problems, particular changes in the structure of the brain, bone abnormalities, vision loss, and heart defects.

Pseudodiastrophic dysplasia (PDD) is an extremely rare and severe skeletal dysplasia associated with prenatal manifestation and early lethality. Phenotypic features include short-limbed short stature at birth, facial dysmorphism, and distinctive skeletal abnormalities including short ribs, mild to moderate platyspondyly, shortened long bones with metaphyseal flaring, elongation of the proximal and middle phalanges with subluxation of the proximal interphalangeal joints, subluxation of the elbow, and talipes equinovarus (summary by Byrne et al., 2020). Based on genetic analysis of patients with a clinical diagnosis of PDD, Byrne et al. (2020) proposed that PDD is likely not a separate genetic disorder, but rather the most severe phenotypic manifestation of skeletal dysplasia arising from defects in proteoglycan (PG) biosynthesis (see MOLECULAR GENETICS).

The dyssegmental dysplasias are lethal forms of neonatal short-limbed dwarfism. Handmaker et al. (1977) coined the term 'dyssegmental dysplasia' because of the marked differences in size and shape of the vertebral bodies (anisospondyly), which he attributed to errors in segmentation. Fasanelli et al. (1985) proposed that there are different forms of dyssegmental dwarfism, a lethal Silverman-Handmaker type (224410) and a less severe Rolland-Desbuquois type. The Rolland-Desbuquois form is lethal in about 40% of patients. Although many patients survive beyond the newborn period, all exhibit neonatal distress (summary by Hennekam et al., 2010).

Langer mesomelic dysplasia (LMD) is characterized by severe limb aplasia or severe hypoplasia of the ulna and fibula, and a thickened and curved radius and tibia. These changes can result in displacement deformities of the hands and feet. Hypoplasia of the mandible is also observed (Langer, 1967). See also Leri-Weill dyschondrosteosis (127300), a less severe phenotype that results from heterozygous defect in the SHOX or SHOXY genes.

Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by contiguous gene deletion of TRPS1, RAD21, and EXT1). Both types of TRPS are characterized by distinctive facial features; ectodermal features (fine, sparse, depigmented, and slow growing hair; dystrophic nails; and small breasts); and skeletal findings (short stature; short feet; brachydactyly with ulnar or radial deviation of the fingers; and early, marked hip dysplasia). TRPS II is characterized by multiple osteochondromas (typically first observed clinically on the scapulae and around the elbows and knees between ages 1 month and 6 years) and an increased risk of mild-to-moderate intellectual disability.

A rare primary bone dysplasia characterized, radiologically, by short, stubby long bones, severely angulated femurs and lesser bowing of other long bones (mild, moderate or no bowing), short and wide iliac wings with horizontal acetabular roofs, platyspondyly and a narrow thorax, clinically manifesting with severe, disproportionate short stature. Regression of femora angulation is observed with advancing age.

A rare genetic primary bone dysplasia disease characterized by progressive osteosclerosis and platyspondyly.

Most females with osteopathia striata with cranial sclerosis (OS-CS) present with macrocephaly and characteristic facial features (frontal bossing, hypertelorism, epicanthal folds, depressed nasal bridge, and prominent jaw). Approximately half have associated features including orofacial clefting and hearing loss, and a minority have some degree of developmental delay (usually mild). Radiographic findings of cranial sclerosis, sclerosis of long bones, and metaphyseal striations (in combination with macrocephaly) can be considered pathognomonic. Males can present with a mild or severe phenotype. Mildly affected males have clinical features similar to affected females, including macrocephaly, characteristic facial features, orofacial clefting, hearing loss, and mild-to-moderate learning delays. Mildly affected males are more likely than females to have congenital or musculoskeletal anomalies. Radiographic findings include cranial sclerosis and sclerosis of the long bones; Metaphyseal striations are more common in males who are mosaic for an AMER1 pathogenic variant. The severe phenotype manifests in males as a multiple-malformation syndrome, lethal in mid-to-late gestation, or in the neonatal period. Congenital malformations include skeletal defects (e.g., polysyndactyly, absent or hypoplastic fibulae), congenital heart disease, and brain, genitourinary, and gastrointestinal anomalies. Macrocephaly is not always present and longitudinal metaphyseal striations have not been observed in severely affected males, except for those who are mosaic for the AMER1 pathogenic variant.

Lenz-Majewski hyperostotic dwarfism is a rare condition characterized by intellectual disability, sclerosing bone dysplasia, distinct craniofacial and dental anomalies, loose skin, and distal limb anomalies, particularly brachydactyly and symphalangism. Patients have multiple radiographic abnormalities due to progressive generalized hyperostosis that affects the cranium, vertebrae, and diaphyses of tubular bones, leading to severe growth retardation (summary by Sousa et al., 2014).

Isotretinoin-like syndrome is a phenocopy of the isotretinoin embryopathy. It has been described in six male patients, three of them being siblings born to nonconsanguineous parents. It has characteristics of the same anomalies as those described after maternal treatment with the drug isotretinoin: malformations of the face (small, malformed, or missing ears, micrognathia, cleft palate), conotruncal heart defects, aortic arch anomalies, and central nervous system anomalies (hydrocephalus and posterior fossa abnormalities). As the syndrome has only been reported in males, X-linked recessive inheritance is possible but autosomal recessive inheritance cannot be ruled out.

The main clinical manifestations of chromosome 18p deletion syndrome are mental retardation, growth retardation, craniofacial dysmorphism including round face, dysplastic ears, wide mouth and dental anomalies, and abnormalities of the limbs, genitalia, brain, eyes, and heart. The round face characteristic in the neonatal period and childhood may change to a long face with linear growth of the height of the face (summary by Tsukahara et al., 2001).

While the majority of individuals with Costello syndrome share characteristic findings affecting multiple organ systems, the phenotypic spectrum is wide, ranging from a milder or attenuated phenotype to a severe phenotype with early lethal complications. Costello syndrome is typically characterized by failure to thrive in infancy as a result of severe postnatal feeding difficulties; short stature; developmental delay or intellectual disability; coarse facial features (full lips, large mouth, full nasal tip); curly or sparse, fine hair; loose, soft skin with deep palmar and plantar creases; papillomata of the face and perianal region; diffuse hypotonia and joint laxity with ulnar deviation of the wrists and fingers; tight Achilles tendons; and cardiac involvement including: cardiac hypertrophy (usually typical hypertrophic cardiomyopathy), congenital heart defect (usually valvar pulmonic stenosis), and arrhythmia (usually supraventricular tachycardia, especially chaotic atrial rhythm/multifocal atrial tachycardia or ectopic atrial tachycardia). Relative or absolute macrocephaly is typical, and postnatal cerebellar overgrowth can result in the development of a Chiari I malformation with associated anomalies including hydrocephalus or syringomyelia. Individuals with Costello syndrome have an approximately 15% lifetime risk for malignant tumors including rhabdomyosarcoma and neuroblastoma in young children and transitional cell carcinoma of the bladder in adolescents and young adults.

Recombinant chromosome 8 syndrome (Rec8 syndrome) is a chromosomal disorder found among individuals of Hispanic descent with ancestry from the San Luis Valley of southern Colorado and northern New Mexico. Affected individuals typically have impaired intellectual development, congenital heart defects, seizures, a characteristic facial appearance with hypertelorism, thin upper lip, anteverted nares, wide face, and abnormal hair whorl, and other manifestations (Sujansky et al., 1993, summary by Graw et al., 2000).

A rare chromosomal anomaly with characteristics of psychomotor developmental delay, facial dysmorphism (trigonocephaly, midface hypoplasia, upslanting palpebral fissures, dysplastic small ears, flat nasal bridge with anteverted nostrils and long philtrum, micrognathia, choanal atresia, short neck), single umbilical artery, omphalocele, inguinal or umbilical hernia, genital abnormalities (hypospadia, cryptorchidism), muscular hypotonia and scoliosis.

Jacobsen syndrome (JBS) is a contiguous gene deletion syndrome with major clinical features of growth retardation, psychomotor retardation, trigonocephaly, divergent intermittent strabismus, epicanthus, telecanthus, broad nasal bridge, short nose with anteverted nostrils, carp-shaped upper lip, retrognathia, low-set dysmorphic ears, bilateral camptodactyly, hammertoes, and isoimmune thrombocytopenia (Fryns et al., 1986, Epstein, 1986).

The pseudoaminopterin syndrome (aminopterin syndrome sine aminopterin; ASSA) is a multiple congenital anomaly disorder characterized by ossification defects of the skull, dysmorphic facial features, delayed development, and variable limb defects. The clinical features resemble the embryopathy caused by maternal treatment with the folic acid antagonist aminopterin, which has been recognized since 1952 (Thiersch, 1952) when aminopterin was used as an abortifacient. The characteristic phenotype of the children who survived infancy after having been exposed to aminopterin or its methyl derivative, methotrexate, in early pregnancy included a very unusual facies, skull anomalies, and skeletal defects (summary by Fraser et al., 1987).

Kabuki syndrome (KS) is characterized by typical facial features (long palpebral fissures with eversion of the lateral third of the lower eyelid; arched and broad eyebrows; short columella with depressed nasal tip; large, prominent, or cupped ears), minor skeletal anomalies, persistence of fetal fingertip pads, mild-to-moderate intellectual disability, and postnatal growth deficiency. Other findings may include: congenital heart defects, genitourinary anomalies, cleft lip and/or palate, gastrointestinal anomalies including anal atresia, ptosis and strabismus, and widely spaced teeth and hypodontia. Functional differences can include: increased susceptibility to infections and autoimmune disorders, seizures, endocrinologic abnormalities (including isolated premature thelarche in females), feeding problems, and hearing loss.

Peters plus syndrome is characterized by anterior chamber eye anomalies, short limbs with broad distal extremities, characteristic facial features, cleft lip/palate, and variable developmental delay / intellectual disability. The most common anterior chamber defect is Peters' anomaly, consisting of central corneal clouding, thinning of the posterior cornea, and iridocorneal adhesions. Cataracts and glaucoma are common. Developmental delay is observed in about 80% of children; intellectual disability can range from mild to severe.

Spastic paraplegia-23 (SPG23) is an autosomal recessive neurologic disorder characterized by childhood-onset spastic paraplegia resulting in gait difficulties and associated with pigmentary abnormalities, including premature graying of the hair and vitiligo-like or hyperpigmented skin lesions. Some patients may also have a peripheral neuropathy (summary by Lee et al., 2017).

MED12-related disorders include the phenotypes of FG syndrome type 1 (FGS1), Lujan syndrome (LS), X-linked Ohdo syndrome (XLOS), Hardikar syndrome (HS), and nonspecific intellectual disability (NSID). FGS1 and LS share the clinical findings of cognitive impairment, hypotonia, and abnormalities of the corpus callosum. FGS1 is further characterized by absolute or relative macrocephaly, tall forehead, downslanted palpebral fissures, small and simple ears, constipation and/or anal anomalies, broad thumbs and halluces, and characteristic behavior. LS is further characterized by large head, tall thin body habitus, long thin face, prominent nasal bridge, high narrow palate, and short philtrum. Carrier females in families with FGS1 and LS are typically unaffected. XLOS is characterized by intellectual disability, blepharophimosis, and facial coarsening. HS has been described in females with cleft lip and/or cleft palate, biliary and liver anomalies, intestinal malrotation, pigmentary retinopathy, and coarctation of the aorta. Developmental and cognitive concerns have not been reported in females with HS. Pathogenic variants in MED12 have been reported in an increasing number of males and females with NSID, with affected individuals often having clinical features identified in other MED12-related disorders.

Marden-Walker syndrome (MWKS) is characterized by psychomotor retardation, a mask-like face with blepharophimosis, micrognathia and a high-arched or cleft palate, low-set ears, kyphoscoliosis, and joint contractures. Other features may include Dandy-Walker malformation with hydrocephalus and vertebral abnormalities (summary by Schrander-Stumpel et al., 1993). There are 2 distal arthrogryposis syndromes with features overlapping those of Marden-Walker syndrome that are also caused by heterozygous mutation in PIEZO2: distal arthrogryposis type 3 (DA3, or Gordon syndrome; 114300) and distal arthrogryposis type 5 (DA5; 108145), which are distinguished by the presence of cleft palate and ocular abnormalities, respectively. McMillin et al. (2014) suggested that the 3 disorders may represent variable expressivity of the same condition.

The cardinal findings of Neuhauser syndrome, also known as MMR syndrome, are impaired intellectual development or developmental delay, megalocornea, hypotonia, prominent forehead, micrognathia, prominent nasal bridge, and thin upper lip or carp-like mouth (Naritomi et al., 1997). Reviews Gutierrez-Amavizca et al. (2013) reviewed published reports and tabulated the clinical features of 35 patients with Neuhauser syndrome. Primary megalocornea and psychomotor delay were present in all patients. Characteristics observed in more than half of patients included hypotonia, growth retardation, abnormal electroencephalography (EEG) and/or seizures, micro- or macrocephaly, brain malformations such as cerebral atrophy and hypoplastic corpus callosum, craniofacial dysmorphisms, cardiac anomalies, osteoarticular abnormalities, and refractive errors. Additional features found at low frequency included primary hypothyroidism, recurrent infections, feeding difficulties, cerebral hypomyelination, dyslipidemia, sensorineural deafness, laryngomalacia, large fleshy and cup-shaped ears, obesity, and cryptorchidism. The authors stated that the classification suggested by Verloes et al. (1993) did not seem to be applicable, and proposed that the diagnosis of Neuhauser syndrome should be made in the presence of intellectual disability and megalocornea in the absence of elevated intraocular pressure, with at least 1 minor feature from among those observed in more than half of patients.

A rare multiple congenital malformation syndrome with characteristics of blepharophimosis, ptosis, dental hypoplasia, hearing impairment and intellectual disability. Abnormal ears, microcephaly, and growth retardation have been reported occasionally. Male patients may show cryptorchidism and scrotal hypoplasia. Most reported cases are sporadic, except the original cases of Ohdo who described two affected sisters and a first cousin, suggesting autosomal recessive inheritance. Autosomal dominant, X-linked- and mitochondrial inheritance have also been suggested.

The C syndrome, also known as Opitz trigonocephaly syndrome, is a malformation syndrome characterized by trigonocephaly, severe mental retardation, hypotonia, variable cardiac defects, redundant skin, and dysmorphic facial features, including upslanted palpebral fissures, epicanthal folds, depressed nasal bridge, and low-set, posteriorly rotated ears (summary by Kaname et al., 2007). C syndrome shows phenotypic overlap with Bohring-Opitz syndrome, or C-like syndrome (605039), a disorder with more severe features than C syndrome, caused by heterozygous mutation in the ASXL1 gene (612990) on chromosome 20q11.

Perlman syndrome (PRLMNS) is an autosomal recessive congenital overgrowth syndrome with similarities to Beckwith-Wiedemann syndrome (BWS; 130650). Affected children are large at birth, are hypotonic, and show organomegaly, characteristic facial dysmorphisms (inverted V-shaped upper lip, prominent forehead, deep-set eyes, broad and flat nasal bridge, and low-set ears), renal anomalies (nephromegaly and hydronephrosis), frequent neurodevelopmental delay, and high neonatal mortality. Perlman syndrome is associated with a high risk of Wilms tumor, with a 64% incidence in infants surviving beyond the neonatal period. The tumor is diagnosed at an earlier age in these individuals compared with sporadic cases (less than 2 years and 3-4 years of age, respectively), and there is a high frequency of bilateral tumors (55%). Histologic examination of the kidneys in children with Perlman syndrome shows frequent nephroblastomatosis, which is a precursor lesion for Wilms tumor (summary by Astuti et al., 2012).

Renpenning syndrome (RENS1) is an X-linked syndromic intellectual developmental disorder with clinically recognizable features. Affected individuals have microcephaly, short stature, small testes, and dysmorphic facies, including tall narrow face, upslanting palpebral fissures, abnormal nasal configuration, cupped ears, and short philtrum. The nose may appear long or bulbous, with overhanging columella. Less consistent manifestations include ocular colobomas, cardiac malformations, cleft palate, and anal anomalies. Stevenson et al. (2005) proposed that the various X-linked mental retardation syndromes due to PQBP1 mutations be combined under the name of Renpenning syndrome.

Toriello-Carey syndrome is a multiple congenital anomaly disorder with variable systemic manifestations, most commonly including mental retardation, agenesis of the corpus callosum, postnatal growth delay, cardiac defects, usually septal defects, distal limb defects, and urogenital anomalies in affected males. Patients have facial dysmorphic features, micrognathia, including full cheeks, hypertelorism, flattened nasal bridge, anteverted nares, and short neck. Not all features are found in all patients and some patients may have additional features such as anal anomalies or hernias (summary by Toriello et al., 2003). In a review of the Toriello-Carey syndrome, Toriello et al. (2016) stated that while corpus callosum abnormalities and micrognathia with highly arched or cleft palate are seen in most patients, other manifestations are widely variable. They noted that etiologic heterogeneity has been observed in reported patients, with at least 20% of patients having chromosome anomalies, and that no good candidate genes have been identified by exome sequencing. The authors commented that this condition might not be a unitary diagnostic entity. They recommended chromosome microarray for any child suspected of having the condition, followed by standard of care by genetic testing.

Wieacker-Wolff syndrome (WRWF) is a severe X-linked recessive neurodevelopmental disorder affecting the central and peripheral nervous systems. It is characterized by onset of muscle weakness in utero (fetal akinesia), which results in arthrogryposis multiplex congenita (AMC) apparent at birth. Affected boys are born with severe contractures, show delayed motor development, facial and bulbar weakness, characteristic dysmorphic facial features, and skeletal abnormalities, such as hip dislocation, scoliosis, and foot deformities. Additional features include global developmental delay with poor or absent speech and impaired intellectual development, feeding difficulties and poor growth, hypotonia, hypogenitalism, and spasticity. Carrier females may be unaffected or have mild features of the disorder (summary by Hirata et al., 2013 and Frints et al., 2019).

The spectrum of MECP2-related phenotypes in females ranges from classic Rett syndrome to variant Rett syndrome with a broader clinical phenotype (either milder or more severe than classic Rett syndrome) to mild learning disabilities; the spectrum in males ranges from severe neonatal encephalopathy to pyramidal signs, parkinsonism, and macroorchidism (PPM-X) syndrome to severe syndromic/nonsyndromic intellectual disability. Females: Classic Rett syndrome, a progressive neurodevelopmental disorder primarily affecting girls, is characterized by apparently normal psychomotor development during the first six to 18 months of life, followed by a short period of developmental stagnation, then rapid regression in language and motor skills, followed by long-term stability. During the phase of rapid regression, repetitive, stereotypic hand movements replace purposeful hand use. Additional findings include fits of screaming and inconsolable crying, autistic features, panic-like attacks, bruxism, episodic apnea and/or hyperpnea, gait ataxia and apraxia, tremors, seizures, and acquired microcephaly. Males: Severe neonatal-onset encephalopathy, the most common phenotype in affected males, is characterized by a relentless clinical course that follows a metabolic-degenerative type of pattern, abnormal tone, involuntary movements, severe seizures, and breathing abnormalities. Death often occurs before age two years.

Bohring-Opitz syndrome (BOS) is characterized by distinctive facial features and posture, growth failure, variable but usually severe intellectual disability, and variable anomalies. The facial features may include microcephaly or trigonocephaly / prominent (but not fused) metopic ridge, hypotonic facies with full cheeks, synophrys, glabellar and eyelid nevus flammeus (simplex), prominent globes, widely set eyes, palate anomalies, and micrognathia. The BOS posture, which is most striking in early childhood and often becomes less apparent with age, is characterized by flexion at the elbows with ulnar deviation and flexion of the wrists and metacarpophalangeal joints. Feeding difficulties in early childhood, including cyclic vomiting, have a significant impact on overall health; feeding tends to improve with age. Seizures are common and typically responsive to standard epileptic medications. Minor cardiac anomalies and transient bradycardia and apnea may be present. Affected individuals may experience recurrent infections, which also tend to improve with age. Isolated case reports suggest that individuals with BOS are at greater risk for Wilms tumor than the general population, but large-scale epidemiologic studies have not been conducted.

Acromegaloid facial appearance (AFA) syndrome is a multiple congenital anomalies/dysmorphic syndrome with a probable autosomal dominant inheritance, characterized by a progressively coarse acromegaloid-like facial appearance with thickening of the lips and intraoral mucosa, large and doughy hands and, in some cases, developmental delay. AFA syndrome appears to be part of a phenotypic spectrum that includes hypertrichotic osteochondrodysplasia, Cantu type and hypertrichosis-acromegaloid facial appearance syndrome.

SHORT syndrome is a mnemonic for short stature, hyperextensibility, ocular depression (deeply set eyes), Rieger anomaly, and teething delay. It is now recognized that the features most consistently observed in SHORT syndrome are mild intrauterine growth restriction (IUGR); mild to moderate short stature; partial lipodystrophy (evident in the face, and later in the chest and upper extremities, often sparing the buttocks and legs); and a characteristic facial gestalt. Insulin resistance may be evident in mid-childhood or adolescence, although diabetes mellitus typically does not develop until early adulthood. Other frequent features include Axenfeld-Rieger anomaly or related ocular anterior chamber dysgenesis, delayed dentition and other dental issues, and sensorineural hearing loss.

Hajdu-Cheney syndrome (HJCYS) is a rare autosomal dominant skeletal disorder characterized by short stature, coarse and dysmorphic facies, bowing of the long bones, and vertebral anomalies. Facial features include hypertelorism, bushy eyebrows, micrognathia, small mouth with dental anomalies, low-set ears, and short neck. There is progressive focal bone destruction, including acroosteolysis and generalized osteoporosis. Additional and variable features include hearing loss, renal cysts, and cardiovascular anomalies (summary by Ramos et al., 1998; Simpson et al., 2011; Isidor et al., 2011).

Cardiofaciocutaneous (CFC) syndrome is characterized by cardiac abnormalities (pulmonic stenosis and other valve dysplasias, septal defects, hypertrophic cardiomyopathy, rhythm disturbances), distinctive craniofacial appearance, and cutaneous abnormalities (including xerosis, hyperkeratosis, ichthyosis, keratosis pilaris, ulerythema ophryogenes, eczema, pigmented moles, hemangiomas, and palmoplantar hyperkeratosis). The hair is typically sparse, curly, fine or thick, woolly or brittle; eyelashes and eyebrows may be absent or sparse. Nails may be dystrophic or fast growing. Some form of neurologic and/or cognitive delay (ranging from mild to severe) is seen in all affected individuals. Neoplasia, mostly acute lymphoblastic leukemia, has been reported in some individuals.

Decreased fetal activity associated with multiple joint contractures, facial anomalies and pulmonary hypoplasia. Ultrasound examination may reveal polyhydramnios, ankylosis, scalp edema, and decreased chest movements (reflecting pulmonary hypoplasia).

Saul-Wilson syndrome (SWS) is a skeletal dysplasia characterized by profound short stature, distinctive craniofacial features, short distal phalanges of fingers and toes, and often clubfoot. Early development (primarily speech and motor) is delayed; cognition is normal. Other findings can include hearing loss (conductive, sensorineural, and mixed), lamellar cataracts, and/or rod-cone retinal dystrophy. To date, 16 affected individuals have been reported.

Barber-Say syndrome (BBRSAY) is a rare congenital condition characterized by severe hypertrichosis, especially of the back, skin abnormalities such as hyperlaxity and redundancy, and facial dysmorphism, including macrostomia, eyelid deformities, ocular telecanthus, abnormal and low-set ears, bulbous nasal tip with hypoplastic alae nasi, and low frontal hairline (summary by Roche et al., 2010).

Shprintzen-Goldberg syndrome (SGS) is characterized by: delayed motor and cognitive milestones and mild-to-moderate intellectual disability; craniosynostosis of the coronal, sagittal, or lambdoid sutures; distinctive craniofacial features; and musculoskeletal findings including olichostenomelia, arachnodactyly, camptodactyly, pectus excavatum or carinatum, scoliosis, joint hypermobility or contractures, pes planus, foot malposition, and C1-C2 spine malformation. Cardiovascular anomalies may include mitral valve prolapse, secundum atrial septal defect, and aortic root dilatation. Minimal subcutaneous fat, abdominal wall defects, and myopia are also characteristic findings.

A rare genetic syndrome featuring connective tissue abnormalities. Clinical signs include brachycephaly, arachnodactyly, receding mandible and joint laxity at the hands and feet.

Andersen-Tawil syndrome (ATS) is characterized by a triad of: episodic flaccid muscle weakness (i.e., periodic paralysis); ventricular arrhythmias and prolonged QT interval; and anomalies including low-set ears, widely spaced eyes, small mandible, fifth-digit clinodactyly, syndactyly, short stature, and scoliosis. Affected individuals present in the first or second decade with either cardiac symptoms (palpitations and/or syncope) or weakness that occurs spontaneously following prolonged rest or following rest after exertion. Mild permanent weakness is common. Mild learning difficulties and a distinct neurocognitive phenotype (i.e., deficits in executive function and abstract reasoning) have been described.

Cornelia de Lange syndrome (CdLS) encompasses a spectrum of findings from mild to severe. Severe (classic) CdLS is characterized by distinctive facial features, growth restriction (prenatal onset; <5th centile throughout life), hypertrichosis, and upper-limb reduction defects that range from subtle phalangeal abnormalities to oligodactyly (missing digits). Craniofacial features include synophrys, highly arched and/or thick eyebrows, long eyelashes, short nasal bridge with anteverted nares, small widely spaced teeth, and microcephaly. Individuals with a milder phenotype have less severe growth, cognitive, and limb involvement, but often have facial features consistent with CdLS. Across the CdLS spectrum IQ ranges from below 30 to 102 (mean: 53). Many individuals demonstrate autistic and self-destructive tendencies. Other frequent findings include cardiac septal defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia.

A rare genetic non-syndromic central nervous system malformation with characteristics of absence of the telencephalon and absent or abnormal diencephalic structures, combined with severe abnormalities of the mesencephalon and cerebellum. Further malformations, for example of the hands and feet, have been described in addition.

Syndromic microphthalmia-9 (MCOPS9), also referred to as pulmonary hypoplasia-diaphragmatic hernia-anophthalmia-cardiac defect, is characterized by bilateral clinical anophthalmia, pulmonary hypoplasia/aplasia, cardiac malformations, and diaphragmatic defects. The phenotype is variable, ranging from isolated clinical anophthalmia or microphthalmia to complex presentations involving the cardiac, pulmonary, diaphragmatic, and renal systems. At its most severe, infants are born without pulmonary structures and die soon after birth (Marcadier et al., 2015).

Van den Ende-Gupta syndrome (VDEGS) is an autosomal recessive disorder characterized by severe contractual arachnodactyly from birth and distinctive facial dysmorphism, including triangular face, malar hypoplasia, narrow nose, everted lips, and blepharophimosis. Skeletal anomalies include slender ribs, hooked clavicles, and dislocated radial head. There is no neurologic involvement (summary by Patel et al., 2014).

Schilbach-Rott syndrome (SBRS) is an autosomal dominant disorder characterized by hypotelorism, epicanthal folds, cleft palate, dysmorphic facies, and hypospadias in males. The phenotype is variable, and mildly impaired intellectual development has been reported (summary by Shkalim et al., 2009).

Al-Gazali syndrome (ALGAZ) is characterized by prenatal growth retardation, skeletal anomalies including joint contractures, camptodactyly, and bilateral talipes equinovarus, small mouth, anterior segment eye anomalies, and early lethality (summary by Ben-Mahmoud et al., 2018).

Emanuel syndrome is characterized by pre- and postnatal growth deficiency, microcephaly, hypotonia, severe developmental delays, ear anomalies, preauricular tags or pits, cleft or high-arched palate, congenital heart defects, kidney abnormalities, and genital abnormalities in males.

Cleft palate as an isolated malformation behaves as an entity distinct from cleft lip with or without cleft palate (see 119530). Dominantly inherited cleft soft palate in 4 generations has been reported (Jenkins and Stady, 1980); see 119570.

Congenital disorders of glycosylation (CDGs) are metabolic deficiencies in glycoprotein biosynthesis that usually cause severe mental and psychomotor retardation. Different forms of CDGs can be recognized by altered isoelectric focusing (IEF) patterns of serum transferrin. For a discussion of the classification of CDGs, see CDG Ia (212065).

Insulin-like growth factor I deficiency (IGF1D) is characterized by severe pre- and postnatal growth failure, sensorineural deafness, and impaired motor and intellectual development (summary by Bonapace et al., 2003).

ASPM primary microcephaly (ASPM-MCPH) is characterized by: (1) significant microcephaly (below -3 SD for age) usually present at birth and always present before age one year and (2) the absence of other congenital anomalies. While developmental milestones are usually normal in young children, older children have variable levels of intellectual disability. Neurologic examination is usually normal except for mild spasticity. Seizures are not common.

Intellectual disability-brachydactyly-Pierre Robin syndrome is a rare developmental defect during embryogenesis syndrome characterized by mild to moderate intellectual disability and phsychomotor delay, Robin sequence (incl. severe micrognathia and soft palate cleft) and distinct dysmorphic facial features (e.g. synophris, short palpebral fissures, hypertelorism, small, low-set, and posteriorly angulated ears, bulbous nose, long/flat philtrum, and bow-shaped upper lip). Skeletal anomalies, such as brachydactyly, clinodactyly, small hands and feet, and oral manifestations (e.g. bifid, short tongue, oligodontia) are also associated. Additional features reported include microcephaly, capillary hemangiomas on face and scalp, ventricular septal defect, corneal clouding, nystagmus and profound sensorineural deafness.

Mandibuloacral dysplasia with type B lipodystrophy (MADB) is a rare autosomal recessive disorder characterized by postnatal growth retardation, craniofacial anomalies such as mandibular hypoplasia, skeletal anomalies such as progressive osteolysis of the terminal phalanges and clavicles, and skin changes such as mottled hyperpigmentation and atrophy. The lipodystrophy is characterized by generalized loss of subcutaneous fat involving the face, trunk, and extremities. Some patients have a progeroid appearance. Metabolic complications associated with insulin resistance have been reported (Schrander-Stumpel et al., 1992; summary by Simha et al., 2003). For a general phenotypic description of lipodystrophy associated with mandibuloacral dysplasia, see MADA (248370).

TXNL4A-related craniofacial disorders comprise a range of phenotypes that includes: isolated choanal atresia; choanal atresia with minor anomalies; and Burn-McKeown syndrome (BMKS), which is characterized by typical craniofacial features (bilateral choanal atresia/stenosis, short palpebral fissures, coloboma of the lower eyelids, prominent nasal bridge with widely spaced eyes, short philtrum, thin vermilion of the upper lip, and prominent ears). Hearing loss is common and cardiac defects and short stature have been reported. Intellectual disability is rare.

The Verloes-David-Pfeiffer mesomelia-synostoses syndrome is an autosomal dominant form of mesomelic dysplasia comprising typical acral synostoses combined with ptosis, hypertelorism, palatal abnormality, congenital heart disease, and ureteral anomalies (summary by Isidor et al., 2009). Mesomelia and synostoses are also cardinal features of the Kantaputra type of mesomelic dysplasia (156232).

RAB18 deficiency is the molecular deficit underlying both Warburg micro syndrome (characterized by eye, nervous system, and endocrine abnormalities) and Martsolf syndrome (characterized by similar – but milder – findings). To date Warburg micro syndrome comprises >96% of reported individuals with genetically defined RAB18 deficiency. The hallmark ophthalmologic findings are bilateral congenital cataracts, usually accompanied by microphthalmia, microcornea (diameter <10), and small atonic pupils. Poor vision despite early cataract surgery likely results from progressive optic atrophy and cortical visual impairment. Individuals with Warburg micro syndrome have severe to profound intellectual disability (ID); those with Martsolf syndrome have mild to moderate ID. Some individuals with RAB18 deficiency also have epilepsy. In Warburg micro syndrome, a progressive ascending spastic paraplegia typically begins with spastic diplegia and contractures during the first year, followed by upper-limb involvement leading to spastic quadriplegia after about age five years, often eventually causing breathing difficulties. In Martsolf syndrome infantile hypotonia is followed primarily by slowly progressive lower-limb spasticity. Hypogonadism – when present – manifests in both syndromes, in males as micropenis and/or cryptorchidism and in females as hypoplastic labia minora, clitoral hypoplasia, and small introitus.

X-linked lethal multiple pterygium syndrome is a rare, genetic, developmental defect during embryogenesis characterized by the typical lethal multiple pterygium syndrome presentation (comprising of multiple pterygia, severe arthrogryposis, cleft palate, cystic hygromata and/or fetal hydrops, skeletal abnormalities and fetal death in the 2nd or 3rd trimester) with an X-linked pattern of inheritance.

The classic features of TARP syndrome are talipes equinovarus, atrial septal defect, Robin sequence (micrognathia, cleft palate, and glossoptosis), and persistent left superior vena cava. Not all patients have all classic features. Some patients have the additional features of central nervous system dysfunction, renal abnormalities, variable cardiac anomalies including hypertrophic obstructive cardiomyopathy, and variable distal limb defects including syndactyly. Most patients die in late prenatal or early postnatal stages (summary by Kaeppler et al., 2018).

Ischiocoxopodopatellar syndrome (ICPPS) is a rare autosomal dominant disorder characterized by a/hypoplasia of the patellas and various anomalies of the pelvis and feet. Pelvic anomalies include bilateral absent or delayed ossification of the ischiopubic junction and infraacetabular axe cut notches. Other major signs are a wide gap between the first and second toes, short fourth and fifth rays of the feet, and pes planus (summary by Bongers et al., 2001). Pediatric-onset pulmonary arterial hypertension may be seen in association with ICPPS (Kerstjens-Frederikse et al., 2013 and Levy et al., 2016).

A rare osteogenesis imperfecta-like disorder, described in two patients to date, with clinical characteristics of persistent wormian bones, blue sclera, mandibular hypoplasia, shallow glenoid fossa, and campomelia. There have been no further descriptions in the literature since 1986.

Cataract-congenital heart disease-neural tube defect syndrome is a multiple congenital anomaly syndrome characterized by sacral neural tube defects resulting in tethered cord, atrial and/or ventricular septal heart defects (that are detected in infancy), bilateral, symmetrical hyperopia, rapidly progressive early childhood cataracts, bilateral aphakic glaucoma, and abnormal facial features (low frontal hairline, small ears, short philtrum, prominent, widely spaced central incisors, and micrognathia). Hypotonia, growth and developmental delay, seizures, and joint limitation are also reported.

Diaphanospondylodysostosis is a rare, recessively inherited, perinatal lethal skeletal disorder. The primary skeletal characteristics include small chest, abnormal vertebral segmentation, and posterior rib gaps containing incompletely differentiated mesenchymal tissue. Consistent craniofacial features include ocular hypertelorism, epicanthal folds, depressed nasal bridge with short nose, and low-set ears. The most commonly described extraskeletal finding is nephroblastomatosis with cystic kidneys, but other visceral findings have been described in some cases (summary by Funari et al., 2010).

Gaucher disease (GD) encompasses a continuum of clinical findings from a perinatal lethal disorder to an asymptomatic type. The identification of three major clinical types (1, 2, and 3) and two other subtypes (perinatal-lethal and cardiovascular) is useful in determining prognosis and management. GD type 1 is characterized by the presence of clinical or radiographic evidence of bone disease (osteopenia, focal lytic or sclerotic lesions, and osteonecrosis), hepatosplenomegaly, anemia and thrombocytopenia, lung disease, and the absence of primary central nervous system disease. GD types 2 and 3 are characterized by the presence of primary neurologic disease; in the past, they were distinguished by age of onset and rate of disease progression, but these distinctions are not absolute. Disease with onset before age two years, limited psychomotor development, and a rapidly progressive course with death by age two to four years is classified as GD type 2. Individuals with GD type 3 may have onset before age two years, but often have a more slowly progressive course, with survival into the third or fourth decade. The perinatal-lethal form is associated with ichthyosiform or collodion skin abnormalities or with nonimmune hydrops fetalis. The cardiovascular form is characterized by calcification of the aortic and mitral valves, mild splenomegaly, corneal opacities, and supranuclear ophthalmoplegia. Cardiopulmonary complications have been described with all the clinical subtypes, although varying in frequency and severity.

Lethal congenital contracture syndrome-2 (LCCS2) is an autosomal recessive disorder characterized by severe multiple congenital contractures with muscle wasting and atrophy. Micrognathia and other craniofacial anomalies, including cleft palate, as well as cardiac defects and enlarged urinary bladder at birth have also been reported. Hydrops fetalis and multiple pterygia are absent. Most patients have died in the neonatal period, although 2 survived to early adolescence (Landau et al., 2003). For a general phenotypic description and a discussion of genetic heterogeneity of LCCS, see LCCS1 (253310).

The X-linked otopalatodigital (X-OPD) spectrum disorders, characterized primarily by skeletal dysplasia, include the following: Otopalatodigital syndrome type 1 (OPD1). Otopalatodigital syndrome type 2 (OPD2). Frontometaphyseal dysplasia type 1 (FMD1). Melnick-Needles syndrome (MNS). Terminal osseous dysplasia with pigmentary skin defects (TODPD). In OPD1, most manifestations are present at birth; females can present with severity similar to affected males, although some have only mild manifestations. In OPD2, females are less severely affected than related affected males. Most males with OPD2 die during the first year of life, usually from thoracic hypoplasia resulting in pulmonary insufficiency. Males who live beyond the first year of life are usually developmentally delayed and require respiratory support and assistance with feeding. In FMD1, females are less severely affected than related affected males. Males do not experience a progressive skeletal dysplasia but may have joint contractures and hand and foot malformations. Progressive scoliosis is observed in both affected males and females. In MNS, wide phenotypic variability is observed; some individuals are diagnosed in adulthood, while others require respiratory support and have reduced longevity. MNS in males results in perinatal lethality in all recorded cases. TODPD, seen only in females, is characterized by a skeletal dysplasia that is most prominent in the digits, pigmentary defects of the skin, and recurrent digital fibromata.

Catel-Manzke syndrome is characterized by the Pierre Robin anomaly, which comprises cleft palate, glossoptosis, and micrognathia, and a unique form of bilateral hyperphalangy in which there is an accessory bone inserted between the second metacarpal and its corresponding proximal phalanx, resulting in radial deviation of the index finger (summary by Manzke et al., 2008).

X-linked infantile spinal muscular atrophy (XL-SMA) is characterized by congenital hypotonia, areflexia, and evidence of degeneration and loss of anterior horn cells (i.e., lower motor neurons) in the spinal cord and brain stem. Often congenital contractures and/or fractures are present. Intellect is normal. Life span is significantly shortened because of progressive ventilatory insufficiency resulting from chest muscle involvement.

Claes-Jensen type of X-linked syndromic intellectual developmental disorder (MRXSCJ) is characterized by impaired intellectual development with substantial clinical heterogeneity in affected males. However, males are usually reported to have short stature, microcephaly, hyperreflexia, and aggressive behavior. In rare cases, female carriers exhibit mildly impaired intellectual development or learning difficulties (summary by Guerra et al., 2020).

Martin-Probst syndrome (MRXSMP) is characterized by congenital sensorineural hearing loss, mild to severe cognitive impairment, short stature, and facial dysmorphism, including telecanthus, hypertelorism, epicanthic folds, broad mouth, and low-set ears. Variable features include renal and genitourinary abnormalities and late-onset pancytopenia (Martin et al., 2000).

X-linked lissencephaly-2 (LISX2) is a developmental disorder characterized by structural brain anomalies, early-onset intractable seizures, severe psychomotor retardation, and ambiguous genitalia. Males are severely affected and often die within the first days or months of life, whereas females may be unaffected or have a milder phenotype (Bonneau et al., 2002). LISX2 is part of a phenotypic spectrum of disorders caused by mutation in the ARX gene comprising a nearly continuous series of developmental disorders ranging from hydranencephaly and lissencephaly to Proud syndrome (300004) to infantile spasms without brain malformations (DEE1; 308350) to syndromic (309510) and nonsyndromic (300419) mental retardation (Kato et al., 2004; Wallerstein et al., 2008). For a general phenotypic description and a discussion of genetic heterogeneity of lissencephaly, see LIS1 (607432).

Lathosterolosis (LATHOS) is an autosomal recessive disorder characterized by a recognizable pattern of multiple congenital anomalies involving axial and appendicular skeleton, liver, central nervous and urogenital systems, and lysosomal storage. It is caused by a defect of cholesterol biosynthesis due to sterol C5-desaturase deficiency (summary by Rossi et al., 2007).

Amish lethal microcephaly is characterized by severe congenital microcephaly and highly elevated 2-ketoglutarate or lactic acidosis. The occipitofrontal circumference is typically more than two standard deviations (occasionally >6 SD) below the mean; anterior and posterior fontanels are closed at birth and facial features are distorted. The average life span of an affected infant is between five and six months among the Lancaster Amish, although an affected Amish-Mennonite child was reported to be living with severe developmental delay at age seven years.

Seckel syndrome is a rare autosomal recessive disorder characterized by growth retardation, microcephaly with mental retardation, and a characteristic facial appearance (Borglum et al., 2001). For a general phenotypic description and a discussion of genetic heterogeneity of Seckel syndrome, see SCKL1 (210600).

Whistling face syndrome is characterized by an atypical facial appearance with anomalies of the hands and feet. Most cases show autosomal dominant inheritance: see distal arthrogryposis 2A (DA2A; 193700). There are rare reports of presumably autosomal recessive inheritance (summary by Altunhan et al., 2010).

Cold-induced sweating syndrome (CISS) and its infantile presentation, Crisponi syndrome(CS) is characterized by dysmorphic features (distinctive facies, lower facial weakness, flexion deformity at the elbows, camptodactyly with fisted hands, misshapen feet, and overriding toes); intermittent contracture of facial and oropharyngeal muscles when crying or being handled with puckering of lips and drooling of foamy saliva often associated with laryngospasm and respiratory distress; excessive startling and opisthotonus-like posturing with unexpected tactile or auditory stimuli; poor suck reflex and severely impaired swallowing; and a scaly erythematous rash. During the first decade of life, children with CISS/CS develop profuse sweating of the face, arms, and chest with ambient temperatures below 18º to 22º C, and with other stimuli including nervousness or ingestion of sweets. Affected individuals sweat very little in hot environments and may feel overheated. Progressive thoracolumbar kyphoscoliosis occurs, requiring intervention in the second decade.

Spondylometaepiphyseal dysplasia, short limb-hand type is an autosomal recessive disorder with clinical and radiologic features of disproportionate short stature, platyspondyly, abnormal epiphyses and metaphyses, shortening of the lower and upper limbs, short and broad fingers, and premature calcifications. The disorder is progressive with respect to the severity of the bowing of the lower limbs and the appearance of calcifications, with some patients being wheelchair-bound from age 11 years (Bargal et al., 2009).

Patients with mutations in the receptor for insulin-like growth factor I show intrauterine growth retardation and postnatal growth failure, resulting in short stature and microcephaly. Other features may include delayed bone age, developmental delay, and dysmorphic features.

Patients with Richieri-Costa-Pereira syndrome display a pattern of anomalies consisting of microstomia, micrognathia, abnormal fusion of the mandible, cleft palate/Robin sequence, absence of lower central incisors, minor ear anomalies, hypoplastic first ray, abnormal tibiae, hypoplastic halluces, and clubfeet. Learning disability is also a common finding (summary by Favaro et al., 2011).

Rhizomelic syndrome, Urbach type is a rare primary bone dysplasia characterized by upper limbs rhizomelia and other skeletal anomalies (e.g. short stature, dislocated hips, digitalization of the thumb with bifid distal phalanx), craniofacial features (e.g. microcephaly, large anterior fontanelle, fine and sparse scalp hair, depressed nasal bridge, high arched palate, micrognathia, short neck), congenital heart defects (e.g. pulmonary stenosis), delayed psychomotor development and mild flexion contractures of elbows. Radiologic evaluation may reveal flared epiphyses, platyspondyly and/or digital anomalies.

Short-rib thoracic dysplasia (SRTD) with or without polydactyly refers to a group of autosomal recessive skeletal ciliopathies that are characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof. SRTD encompasses Ellis-van Creveld syndrome (EVC) and the disorders previously designated as Jeune syndrome or asphyxiating thoracic dystrophy (ATD), short rib-polydactyly syndrome (SRPS), and Mainzer-Saldino syndrome (MZSDS). Polydactyly is variably present, and there is phenotypic overlap in the various forms of SRTDs, which differ by visceral malformation and metaphyseal appearance. Nonskeletal involvement can include cleft lip/palate as well as anomalies of major organs such as the brain, eye, heart, kidneys, liver, pancreas, intestines, and genitalia. Some forms of SRTD are lethal in the neonatal period due to respiratory insufficiency secondary to a severely restricted thoracic cage, whereas others are compatible with life (summary by Huber and Cormier-Daire, 2012 and Schmidts et al., 2013). There is phenotypic overlap with the cranioectodermal dysplasias (Sensenbrenner syndrome; see CED1, 218330). For a discussion of genetic heterogeneity of short-rib thoracic dysplasia, see SRTD1 (208500).

Bartsocas-Papas syndrome-1 (BPS1) is an autosomal recessive disorder characterized by multiple popliteal pterygia, ankyloblepharon, filiform bands between the jaws, cleft lip and palate, and syndactyly. Early lethality is common, although survival into childhood and beyond has been reported (summary by Mitchell et al., 2012). Genetic Heterogeneity of Bartsocas-Papas Syndrome Bartsocas-Papas syndrome-2 (BPS2) is caused by mutation in the CHUK gene (600664). A less severe form of popliteal pterygium syndrome (PPS; 119500) is caused by mutation in the IRF6 gene (607199).

Gillessen-Kaesbach-Nishimura syndrome is an autosomal recessive multiple congenital anomaly disorder characterized by skeletal dysplasia, dysmorphic facial features, and variable visceral abnormalities, including polycystic kidneys, diaphragmatic hernia, lung hypoplasia, and congenital heart defects. It may be lethal in utero or early in life. The disorder is at the severe end of the phenotypic spectrum of congenital disorders of glycosylation (summary by Tham et al., 2016).

Syndrome with characteristics of pelviscapular dysplasia with epiphyseal abnormalities, congenital dwarfism and facial dysmorphism. The facial dysmorphism has manifestations of frontal bossing, hypertelorism, narrow palpebral fissures, deep-set eyes, strabismus, low-set posteriorly rotated and malformed ears, dysplasia of conchae, a small chin, a short neck with redundant skin folds, and a low hairline. Intelligence may vary from normal to moderately impaired. Radiographic features comprise aplasia of the body of the scapula, hypoplasia of the iliac bone, humeroradial synostosis, dislocation of the femoral heads, and moderate brachydactyly. Mutations in the TBX15 gene have been identified as potentially causative. Pelviscapular dysplasia is phenotypically similar to pelvis-shoulder dysplasia.

Raine syndrome (RNS) is a neonatal osteosclerotic bone dysplasia of early and aggressive onset that usually results in death within the first few weeks of life, although there have been some reports of survival into childhood. Radiographic studies show a generalized increase in the density of all bones and a marked increase in the ossification of the skull. The increased ossification of the basal structures of the skull and facial bones underlies the characteristic facial features, which include narrow prominent forehead, proptosis, depressed nasal bridge, and midface hypoplasia. Periosteal bone formation is also characteristic of this disorder and differentiates it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias. The periosteal bone formation typically extends along the diaphysis of long bones adjacent to areas of cellular soft tissue (summary by Simpson et al., 2009). Some patients survive infancy (Simpson et al., 2009; Fradin et al., 2011).

Multicentric osteolysis nodulosis and arthropathy (MONA) is a skeletal dysplasia characterized by progressive osteolysis (particularly of the carpal and tarsal bones), osteoporosis, subcutaneous nodules on the palms and soles, and progressive arthropathy (joint contractures, pain, swelling, and stiffness). Other manifestations include coarse facies, pigmented skin lesions, cardiac defects, and corneal opacities. Onset is usually between ages six months and six years (range: birth to 11 years).

Omodysplasia-1 (OMOD1) is a rare autosomal recessive skeletal dysplasia characterized by severe congenital micromelia with shortening and distal tapering of the humeri and femora to give a club-like appearance. Typical facial features include a prominent forehead, frontal bossing, short nose with a depressed broad bridge, short columella, anteverted nostrils, long philtrum, and small chin. Variable findings are cryptorchidism, hernias, congenital heart defects, and cognitive delay (Elcioglu et al., 2004; Albano et al., 2007). Genetic Heterogeneity of Omodysplasia Also see omodysplasia-2 (OMOD2; 164745), an autosomal dominant form of the disorder in which abnormalities are limited to the upper limbs. The facial changes and typical growth defect of the distal humerus with complex deformity of the elbows appear to be similar in both entities (Baxova et al., 1994).

Mosaic variegated aneuploidy (MVA) syndrome is a rare disorder in which some cells in the body have an abnormal number of chromosomes instead of the usual 46 chromosomes, a situation known as aneuploidy. Most commonly, cells have an extra chromosome, which is called trisomy, or are missing a chromosome, which is known as monosomy. In MVA syndrome, some cells are aneuploid and others have the normal number of chromosomes, which is a phenomenon known as mosaicism. Typically, at least one-quarter of cells in affected individuals have an abnormal number of chromosomes. Because the additional or missing chromosomes vary among the abnormal cells, the aneuploidy is described as variegated.\n\nThere are at least three types of MVA syndrome, each with a different genetic cause. Type 1 is the most common and displays the classic signs and symptoms described above. Type 2 appears to have slightly different signs and symptoms than type 1, although the small number of affected individuals makes it difficult to define its characteristic features. Individuals with MVA syndrome type 2 grow slowly before and after birth; however, their head size is typically normal. Some people with MVA syndrome type 2 have unusually short arms. Individuals with MVA syndrome type 2 do not seem to have an increased risk of cancer. Another form of MVA syndrome is characterized by a high risk of developing Wilms tumor. Individuals with this form may also have other signs and symptoms typical of MVA syndrome type 1.\n\nIn MVA syndrome, growth before birth is slow (intrauterine growth restriction). After birth, affected individuals continue to grow at a slow rate and are shorter than average. In addition, they typically have an unusually small head size (microcephaly). Another common feature of MVA syndrome is an increased risk of developing cancer in childhood. Cancers that occur most frequently in affected individuals include a cancer of muscle tissue called rhabdomyosarcoma, a form of kidney cancer known as Wilms tumor, and a cancer of the blood-forming tissue known as leukemia.\n\nLess commonly, people with MVA syndrome have eye abnormalities or distinctive facial features, such as a broad nasal bridge and low-set ears. Some affected individuals have brain abnormalities, the most common of which is called Dandy-Walker malformation. Intellectual disability, seizures, and other health problems can also occur in people with MVA syndrome.

Clinical features of atelosteogenesis type 2 (AO2) include rhizomelic limb shortening with normal-sized skull, hitchhiker thumbs, small chest, protuberant abdomen, cleft palate, and distinctive facial features (midface retrusion, depressed nasal bridge, epicanthus, micrognathia). Other typical findings are ulnar deviation of the fingers, gap between the first and second toes, and clubfoot. AO2 is usually lethal at birth or shortly thereafter due to pulmonary hypoplasia and tracheobronchomalacia. However, it exists in a continuous phenotypic spectrum with diastrophic dysplasia, and long-term survivors have been reported.

STAC3 disorder is characterized by congenital myopathy, musculoskeletal involvement of the trunk and extremities, feeding difficulties, and delayed motor milestones. Most affected individuals have weakness with myopathic facies, scoliosis, kyphosis or kyphoscoliosis, and contractures. Other common findings are ptosis, abnormalities of the palate (including cleft palate), and short stature. Risk for malignant hyperthermia susceptibility and restrictive lung disease are increased. Intellect is typically normal. Originally described in individuals from the Lumbee Native American tribe (an admixture of Cheraw Indian, English, and African American ancestry) in the state of North Carolina and reported as Native American myopathy, STAC3 disorder has now been identified in numerous other populations worldwide.

Cerebrooculofacioskeletal syndrome is a severe, progressive neurologic disorder characterized by prenatal onset of arthrogryposis, microcephaly, and growth failure. Postnatal features include severe developmental delay, congenital cataracts (in some), and marked UV sensitivity of the skin. Survival beyond 6 years of age is rare. COFS represents the severe end of the spectrum of disorders caused by mutations in nucleotide excision repair (NER) genes, with Cockayne syndrome and xeroderma pigmentosum being milder NER-related phenotypes (summary by Drury et al., 2014). For a phenotypic description and a discussion of genetic heterogeneity of cerebrooculofacioskeletal syndrome, see COFS1 (214150).

NOTCH3-related lateral meningocele syndrome (LMS) is characterized by multiple lateral spinal meningoceles (protrusions of the arachnoid and dura through spinal foramina), distinctive facial features, joint hyperextensibility, hypotonia, and skeletal, cardiac, and urogenital anomalies. Neurologic sequelæ of the meningoceles depend on size and location and can include neurogenic bladder, paresthesia, back pain, and/or paraparesis. Other neurologic findings can include Chiari I malformation, syringomyelia, and rarely, hydrocephalus. Additional findings of LMS include developmental delay, mixed or conductive hearing loss, and cleft palate. Skeletal abnormalities may include scoliosis, vertebral fusion, scalloping of vertebrae, and wormian bones. Infants may demonstrate feeding difficulties with poor weight gain.

Thickened earlobes-conductive deafness syndrome is characterized by microtia with thickened ear lobes, micrognathia and conductive hearing loss due to congenital ossicular anomalies. It has been described in two families. The mode of inheritance is autosomal dominant.

Cornelia de Lange syndrome (CdLS) encompasses a spectrum of findings from mild to severe. Severe (classic) CdLS is characterized by distinctive facial features, growth restriction (prenatal onset; <5th centile throughout life), hypertrichosis, and upper-limb reduction defects that range from subtle phalangeal abnormalities to oligodactyly (missing digits). Craniofacial features include synophrys, highly arched and/or thick eyebrows, long eyelashes, short nasal bridge with anteverted nares, small widely spaced teeth, and microcephaly. Individuals with a milder phenotype have less severe growth, cognitive, and limb involvement, but often have facial features consistent with CdLS. Across the CdLS spectrum IQ ranges from below 30 to 102 (mean: 53). Many individuals demonstrate autistic and self-destructive tendencies. Other frequent findings include cardiac septal defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia.

Cerebrooculofacioskeletal syndrome-4 (COFS4) is a severe autosomal recessive disorder characterized by growth retardation, dysmorphic facial features, arthrogryposis, and neurologic abnormalities. Cellular studies show a defect in both transcription-coupled and global genome nucleotide excision repair (TC-NER and GG-NER) (summary by Jaspers et al., 2007 and Kashiyama et al., 2013). For a discussion of genetic heterogeneity of cerebrooculofacioskeletal syndrome, see 214150.

Any COFS syndrome in which the cause of the disease is a mutation in the ERCC2 gene.

Congenital deafness with labyrinthine aplasia, microtia, and microdontia (LAMM syndrome) is characterized by: profound bilateral congenital sensorineural deafness associated with inner ear anomalies (most often bilateral complete labyrinthine aplasia); microtia (type I) that is typically bilateral (although unilateral microtia and normal external ears are observed on occasion); and microdontia (small teeth). Individuals with LAMM syndrome commonly have motor delays during infancy presumably due to impaired balance from inner ear (vestibular) abnormalities. Growth, physical development, and cognition are normal.

Phelan-McDermid syndrome is characterized by neonatal hypotonia, absent to severely delayed speech, developmental delay, and minor dysmorphic facial features. Most affected individuals have moderate to profound intellectual disability. Other features include large fleshy hands, dysplastic toenails, and decreased perspiration that results in a tendency to overheat. Normal stature and normal head size distinguishes Phelan-McDermid syndrome from other autosomal chromosome disorders. Behavior characteristics include mouthing or chewing non-food items, decreased perception of pain, and autism spectrum disorder or autistic-like affect and behavior.

KAT6B disorders include genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) which are part of a broad phenotypic spectrum with variable expressivity; individuals presenting with a phenotype intermediate between GPS and SBBYSS have been reported. Both phenotypes are characterized by some degree of global developmental delay / intellectual disability; hypotonia; genital abnormalities; and skeletal abnormalities including patellar hypoplasia/agenesis, flexion contractures of the knees and/or hips, and anomalies of the digits, spine, and/or ribs. Congenital heart defects, small bowel malrotation, feeding difficulties, slow growth, cleft palate, hearing loss, and dental anomalies have been observed in individuals with either phenotype.

Noonan syndrome (NS) is characterized by characteristic facies, short stature, congenital heart defect, and developmental delay of variable degree. Other findings can include broad or webbed neck, unusual chest shape with superior pectus carinatum and inferior pectus excavatum, cryptorchidism, varied coagulation defects, lymphatic dysplasias, and ocular abnormalities. Although birth length is usually normal, final adult height approaches the lower limit of normal. Congenital heart disease occurs in 50%-80% of individuals. Pulmonary valve stenosis, often with dysplasia, is the most common heart defect and is found in 20%-50% of individuals. Hypertrophic cardiomyopathy, found in 20%-30% of individuals, may be present at birth or develop in infancy or childhood. Other structural defects include atrial and ventricular septal defects, branch pulmonary artery stenosis, and tetralogy of Fallot. Up to one fourth of affected individuals have mild intellectual disability, and language impairments in general are more common in NS than in the general population.

Wiedemann-Steiner syndrome (WSS) is characterized by developmental delay, intellectual disability, and characteristic facial features, with or without additional congenital anomalies. The facial features include thick eyebrows with lateral flare, vertically narrow and downslanted palpebral fissures, widely spaced eyes, long eyelashes, wide nasal bridge, broad nasal tip, thin vermilion of the upper lip, and thick scalp hair. About 60% of affected individuals have hypertrichosis cubiti ("hairy elbows"), which was once thought to be pathognomic for the syndrome, with a majority having hypertrichosis of other body parts. Other clinical features include feeding difficulties, prenatal and postnatal growth restriction, epilepsy, ophthalmologic anomalies, congenital heart defects, hand anomalies (such as brachydactyly and clinodactyly), hypotonia, vertebral anomalies (especially fusion anomalies of the cervical spine), renal and uterine anomalies, immune dysfunction, brain malformations, and dental anomalies.

Autosomal recessive lethal congenital contracture syndrome (LCCS) is the most severe, neonatally lethal, form of arthrogryposis (see 108120), a disorder characterized by congenital nonprogressive joint contractures. The contractures can involve the upper or lower limbs and/or the vertebral column, leading to various degrees of flexion or extension limitations evident at birth (summary by Markus et al., 2012). Genetic Heterogeneity of Lethal Congenital Contracture Syndrome See also lethal congenital contracture syndrome-2 (LCCS2; 607598), caused by mutation in the ERBB3 gene (190151); LCCS3 (611369), caused by mutation in the PIP5K1C gene (606102); LCCS4 (614915), caused by mutation in the MYBPC1 gene (160794); LCCS5 (615368), caused by mutation in the DNM2 gene (602378); LCCS6 (616248), caused by mutation in the ZBTB42 gene (613915); LCCS7 (616286), caused by mutation in the CNTNAP1 gene (602346); LCCS8 (616287), caused by mutation in the ADCY6 gene (600294); LCCS9 (616503), caused by mutation in the ADGRG6 gene (612243); LCCS10 (617022), caused by mutation in the NEK9 gene (609798); and LCCS11 (617194), caused by mutation in the GLDN gene (608603).

Lethal multiple pterygium syndrome has many of the same signs and symptoms as the Escobar type. In addition, affected fetuses may develop a buildup of excess fluid in the body (hydrops fetalis) or a fluid-filled sac typically found on the back of the neck (cystic hygroma). Individuals with this type have severe arthrogryposis. Lethal multiple pterygium syndrome is associated with abnormalities such as underdevelopment (hypoplasia) of the heart, lung, or brain; twisting of the intestines (intestinal malrotation); kidney abnormalities; an opening in the roof of the mouth (a cleft palate); and an unusually small head size (microcephaly). Affected individuals may also develop a hole in the muscle that separates the abdomen from the chest cavity (the diaphragm), a condition called a congenital diaphragmatic hernia. Lethal multiple pterygium syndrome is typically fatal in the second or third trimester of pregnancy.\n\nIn people with multiple pterygium syndrome, Escobar type, the webbing typically affects the skin of the neck, fingers, forearms, inner thighs, and backs of the knee. People with this type may also have arthrogryposis. A side-to-side curvature of the spine (scoliosis) is sometimes seen. Affected individuals may also have respiratory distress at birth due to underdeveloped lungs (lung hypoplasia). People with multiple pterygium syndrome, Escobar type usually have distinctive facial features including droopy eyelids (ptosis), outside corners of the eyes that point downward (downslanting palpebral fissures), skin folds covering the inner corner of the eyes (epicanthal folds), a small jaw, and low-set ears. Males with this condition can have undescended testes (cryptorchidism). This condition does not worsen after birth, and affected individuals typically do not have muscle weakness later in life.\n\nThe two forms of multiple pterygium syndrome are differentiated by the severity of their symptoms. Multiple pterygium syndrome, Escobar type (sometimes referred to as Escobar syndrome) is the milder of the two types. Lethal multiple pterygium syndrome is fatal before birth or very soon after birth.\n\nMultiple pterygium syndrome is a condition that is evident before birth with webbing of the skin (pterygium) at the joints and a lack of muscle movement (akinesia) before birth. Akinesia frequently results in muscle weakness and joint deformities called contractures that restrict the movement of joints (arthrogryposis). As a result, multiple pterygium syndrome can lead to further problems with movement such as arms and legs that cannot fully extend.

Say-Barber-Miller syndrome is characterised by the association of unusual facial features, microcephaly, developmental delay, and severe postnatal growth retardation.

Microcephaly-micromelia syndrome (MIMIS) is a severe autosomal recessive disorder that usually results in death in utero or in the perinatal period. Affected individuals have severe growth retardation with microcephaly and variable malformations of the limbs, particularly the upper limbs. Defects include radial ray anomalies, malformed digits, and clubfeet (summary by Evrony et al., 2017).

Retinitis pigmentosa with or without skeletal anomalies (RPSKA) is characterized by retinal degeneration, brachydactyly, craniofacial abnormalities, short stature, and neurologic defects. Night blindness occurs around 10 years of age, followed by restriction of visual fields. Brachydactyly affects primarily the distal phalanges. Craniofacial abnormalities include frontal bossing, downslanting palpebral fissures, large columella, hypoplastic nares, micrognathia, and large low-set ears (summary by Xu et al., 2017).

A rare syndrome characterised by mesomelic shortening and bowing of the limbs, camptodactyly, skin dimpling and cleft palate with retrognathia and mandibular hypoplasia. It has been described in a brother and sister born to consanguineous parents. Transmission is autosomal recessive.

The primary characteristics of the Frank-ter Haar syndrome (FTHS) are brachycephaly, wide fontanels, prominent forehead, hypertelorism, prominent eyes, macrocornea with or without glaucoma, full cheeks, small chin, bowing of the long bones, and flexion deformity of the fingers. Protruding, simple ears and prominent coccyx are also regarded as important diagnostic signs (summary by Maas et al., 2004). Borrone syndrome was described as a severe progressive multisystem disorder with features overlapping those of FTHS, including thick skin, acne conglobata, osteolysis, gingival hypertrophy, brachydactyly, camptodactyly, and mitral valve prolapse. Although it was initially thought to be a distinct phenotype, mutations in the FTHS-associated gene SH3PXD2B have been identified in patients diagnosed with Borrone syndrome. The earlier differential description was attributed to phenotypic variability as well as to differences in the ages at which patients were examined (Wilson et al., 2014).

Treacher Collins syndrome (TCS) is characterized by bilateral and symmetric downslanting palpebral fissures, malar hypoplasia, micrognathia, and external ear abnormalities. Hypoplasia of the zygomatic bones and mandible can cause significant feeding and respiratory difficulties. About 40%-50% of individuals have conductive hearing loss attributed most commonly to malformation of the ossicles and hypoplasia of the middle ear cavities. Inner ear structures tend to be normal. Other, less common abnormalities include cleft palate and unilateral or bilateral choanal stenosis or atresia. Typically intellect is normal.

Kaufman oculocerebrofacial syndrome (KOS) is characterized by developmental delay, severe intellectual disability, and distinctive craniofacial features. Most affected children have prenatal-onset microcephaly, hypotonia, and growth deficiency. Feeding issues, ocular abnormalities, hearing impairment, and respiratory tract abnormalities are common. Ocular abnormalities can include structural abnormalities (microcornea or microphthalmia, coloboma, optic nerve hypoplasia), refractive errors (myopia ± astigmatism, hyperopia), strabismus, and entropion. Both conductive and sensorineural hearing loss have been reported as well as mixed conductive-sensorineural hearing loss of variable severity. Breathing problems can lead to prolonged hospitalization after birth in more than half of individuals. Less common findings include ectodermal abnormalities, cardiac manifestations, urogenital abnormalities, seizures, and skeletal abnormalities.

Stromme syndrome is an autosomal recessive congenital disorder affecting multiple systems with features of a ciliopathy. Affected individuals typically have some type of intestinal atresia, variable ocular abnormalities, microcephaly, and sometimes involvement of other systems, including renal and cardiac. In some cases, the condition is lethal in early life, whereas other patients show normal survival with or without mild cognitive impairment (summary by Filges et al., 2016).

With the current widespread use of multigene panels and comprehensive genomic testing, it has become apparent that the phenotypic spectrum of EPG5-related disorder represents a continuum. At the most severe end of the spectrum is classic Vici syndrome (defined as a neurodevelopmental disorder with multisystem involvement characterized by the combination of agenesis of the corpus callosum, cataracts, hypopigmentation, cardiomyopathy, combined immunodeficiency, microcephaly, and failure to thrive); at the milder end of the spectrum are attenuated neurodevelopmental phenotypes with variable multisystem involvement. Median survival in classic Vici syndrome appears to be 24 months, with only 10% of children surviving longer than age five years; the most common causes of death are respiratory infections as a result of primary immunodeficiency and/or cardiac insufficiency resulting from progressive cardiac failure. No data are available on life span in individuals at the milder end of the spectrum.

Hypoparathyroidism-retardation-dysmorphism syndrome (HRDS) is an autosomal recessive multisystem disorder characterized by intrauterine and postnatal growth retardation, infantile-onset hypoparathyroidism that can result in severe hypocalcemic seizures, dysmorphic facial features, and developmental delay (summary by Padidela et al., 2009 and Ratbi et al., 2015).

Hypomandibular faciocranial syndrome consists of craniosynostosis, prominent eyes, deficient midface and zygomatic arches, short nose with anteverted nares, protruding lower face, minute oral aperture, persistent buccopharyngeal membrane, severe mandibular hypoplasia, and various extracephalic anomalies (summary by Gorlin et al., 2001).

Hydrolethalus-1 (HLS1) is an autosomal recessive lethal malformation syndrome characterized by hydrocephaly with absent upper midline structures of the brain, micrognathia, and polydactyly. Various other features such as cleft lip or palate, club feet, anomalies of the ears, eyes, and nose, keyhole-shaped defect in the occipital bone, abnormal genitalia, and congenital heart and respiratory organ defects have also been observed in affected individuals. Affected individuals are stillborn or die shortly after birth (summary by Mee et al., 2005). Genetic Heterogeneity of Hydrolethalus Syndrome See also HLS2 (614120), caused by mutation in the KIF7 gene (611254) on chromosome 15q26.

A rare genetic disease characterized by the presence of Müllerian duct derivatives (rudimentary uterus, fallopian tubes, and atretic vagina) and other genital anomalies (cryptorchidism, micropenis) in male newborns, intestinal and pulmonary lymphangiectasia, protein-losing enteropathy, hepatomegaly, and renal anomalies. Postaxial polydactyly, facial dysmorphism (including broad nasal bridge, bulbous nasal tip, long and prominent upper lip with smooth philtrum, hypertrophic alveolar ridges, and mild retrognathia, among other features), and short limbs have also been described. The syndrome is fatal in infancy.

Immunodeficiency-59 and hypoglycemia (IMD59) is an autosomal recessive primary immunologic disorder characterized by combined immunodeficiency and recurrent septic infections of the respiratory tract, skin, and mucous membranes, as well as disturbed glucose metabolism. Granulocytopenia and B-cell and dendritic cell deficiency are present (Haapaniemi et al., 2017).

A rare multiple congenital anomalies/dysmorphic syndrome with characteristics of male, 46,XY gonadal dysgenesis, cleft palate, micrognathia, conotruncal heart defects and unspecific skeletal, brain and kidney anomalies.

Lethal faciocardiomelic dysplasia is an extremely rare polymalformative syndrome. It was described only once, in 1975, in 3 affected males in a sibship of 13, from second-cousin parents. Patients were all of low birth weight, had microretrognathia, microstomia, and microglossia, hypoplasia of the radius and ulna with radial deviation of the hands, simian creases and hypoplasia of fingers I and V, hypoplasia of the fibula and tibia with talipes and wide space between toes I and II, and severe malformation of the left heart which may have been responsible for death of all 3 in the first week or so of life.

The proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome is a rare, autosomal recessive, usually prenatally lethal disorder characterized by hydranencephaly, a distinctive glomerular vasculopathy in the central nervous system and retina, and diffuse ischemic lesions of the brain stem, basal ganglia, and spinal cord with calcifications. It is usually diagnosed by ultrasound between 26 and 33 weeks' gestation (summary by Meyer et al., 2010). Rarely, affected individuals may survive, but are severely impaired with almost no neurologic development (Kvarnung et al., 2016).

Silverman-Handmaker dyssegmental dysplasia (DDSH) is a lethal autosomal recessive skeletal dysplasia with anisospondyly and micromelia. Individuals with DDSH also have a flat face, micrognathia, cleft palate and reduced joint mobility, and frequently have an encephalocele. The endochondral growth plate is short, the calcospherites (spherical calcium-phosphorus crystals produced by hypertrophic chondrocytes) are unfused, and there is mucoid degeneration of the resting cartilage (summary by Arikawa-Hirasawa et al., 2001).

Rhizomelic chondrodysplasia punctata (RCDP) is a peroxisomal disorder characterized by disproportionately short stature primarily affecting the proximal parts of the extremities, a typical facial appearance including a broad nasal bridge, epicanthus, high-arched palate, dysplastic external ears, and micrognathia, congenital contractures, characteristic ocular involvement, dwarfism, and severe mental retardation with spasticity. Biochemically, plasmalogen synthesis and phytanic acid alpha-oxidation are defective. Most patients die in the first decade of life. RCDP1 (215100) is the most frequent form of RCDP (summary by Wanders and Waterham, 2005). Whereas RCDP1 is a peroxisomal biogenesis disorder (PBD), RCDP2 is classified as a single peroxisome enzyme deficiency (Waterham and Ebberink, 2012). For a discussion of genetic heterogeneity of rhizomelic chondrodysplasia punctata, see 215100.

Mitochondrial complex IV deficiency nuclear type 5 (MC4DN5) is an autosomal recessive severe metabolic multisystemic disorder with onset in infancy. Features include delayed psychomotor development, impaired intellectual development with speech delay, mild dysmorphic facial features, hypotonia, ataxia, and seizures. There is increased serum lactate and episodic hypoglycemia. Some patients may have cardiomyopathy, abnormal breathing, or liver abnormalities, reflecting systemic involvement. Brain imaging shows lesions in the brainstem and basal ganglia, consistent with a diagnosis of Leigh syndrome (see 256000). Affected individuals tend to have episodic metabolic and/or neurologic crises in early childhood, which often lead to early death (summary by Debray et al., 2011). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.

Temtamy syndrome is a mental retardation/multiple congenital anomaly syndrome characterized by variable craniofacial dysmorphism, ocular coloboma, seizures, and brain abnormalities, including abnormalities of the corpus callosum and thalamus (summary by Akizu et al., 2013).

Yunis-Varon syndrome (YVS) is a severe autosomal recessive disorder characterized by skeletal defects, including cleidocranial dysplasia and digital anomalies, and severe neurologic involvement with neuronal loss. Enlarged cytoplasmic vacuoles are found in neurons, muscle, and cartilage. The disorder is usually lethal in infancy (summary by Campeau et al., 2013).

7q11.23 duplication syndrome is characterized by delayed motor, speech, and social skills in early childhood; neurologic abnormalities (hypotonia, adventitious movements, and abnormal gait and station); speech sound disorders including motor speech disorders (childhood apraxia of speech and/or dysarthria) and phonologic disorders; behavior problems including anxiety disorders (especially social anxiety disorder [social phobia]), selective mutism, attention-deficit/hyperactivity disorder, oppositional disorders, physical aggression, and autism spectrum disorder; and intellectual disability in some individuals. Distinctive facial features are common. Cardiovascular disease includes dilatation of the ascending aorta. Approximately 30% of individuals have one or more congenital anomalies.

Stickler syndrome is a connective tissue disorder that can include ocular findings of myopia, cataract, and retinal detachment; hearing loss that is both conductive and sensorineural; midfacial underdevelopment and cleft palate (either alone or as part of the Robin sequence); and mild spondyloepiphyseal dysplasia and/or precocious arthritis. Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity.

Primary microcephaly (MCPH) is a clinical diagnosis made when an individual has a head circumference more than 3 standard deviations below the age- and sex-matched population mean and mental retardation, with no other associated malformations and with no apparent etiology. Most cases of primary microcephaly show an autosomal recessive mode of inheritance (summary by Woods et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of primary microcephaly, see MCPH1 (251200).

In WDR62 primary microcephaly (WDR62-MCPH), microcephaly (occipitofrontal circumference [OFC] = -2 SD) is usually present at birth, but in some instances becomes evident later in the first year of life. Growth is otherwise normal. Except for brain malformations in most affected individuals, no other congenital malformations are observed. Central nervous system involvement can include delayed motor development, mild-to-severe intellectual disability (ID), behavior problems, epilepsy, spasticity, and ataxia.

Poikiloderma with neutropenia (PN) is characterized by an inflammatory eczematous rash (ages 6-12 months) followed by post-inflammatory poikiloderma (age >2 years) and chronic noncyclic neutropenia typically associated with recurrent sinopulmonary infections in the first two years of life and (often) bronchiectasis. There is increased risk for myelodysplastic syndrome and, rarely, acute myelogenous leukemia. Other ectodermal findings include nail dystrophy and palmar/plantar hyperkeratosis. Most affected individuals also have reactive airway disease and some have short stature, hypogonadotropic hypogonadism, midfacial retrusion, calcinosis cutis, and non-healing skin ulcers.

Rhizomelic chondrodysplasia punctata type 1 (RCDP1), a peroxisome biogenesis disorder (PBD) has a classic (severe) form and a nonclassic (mild) form. Classic (severe) RCDP1 is characterized by proximal shortening of the humerus (rhizomelia) and to a lesser degree the femur, punctate calcifications in cartilage with epiphyseal and metaphyseal abnormalities (chondrodysplasia punctata, or CDP), coronal clefts of the vertebral bodies, and cataracts that are usually present at birth or appear in the first few months of life. Birth weight, length, and head circumference are often at the lower range of normal; postnatal growth deficiency is profound. Intellectual disability is severe, and the majority of children develop seizures. Most affected children do not survive the first decade of life; a proportion die in the neonatal period. Nonclassic (mild) RCDP1 is characterized by congenital or childhood cataracts, CDP or infrequently, chondrodysplasia manifesting only as mild epiphyseal changes, variable rhizomelia, and milder intellectual disability and growth restriction than classic RCDP1.

Blomstrand chondrodysplasia is an autosomal recessive disorder characterized by short limbs, polyhydramnios, hydrops fetalis, facial anomalies, increased bone density, and advanced skeletal maturation (summary by Loshkajian et al., 1997).

Cenani-Lenz syndactyly syndrome (CLSS) is an autosomal recessive disorder characterized mainly by anomalies of distal limb development, with fusion and disorganization of metacarpal and phalangeal bones, radius and ulnar shortening, radioulnar synostosis, and severe syndactyly of hands and feet. Mild facial dysmorphism is present in most patients. Kidney anomalies, including renal agenesis and hypoplasia, occur in over half of patients (summary by Li et al., 2010).

Bowen-Conradi syndrome (BWCNS) is an autosomal recessive disorder characterized by severely impaired prenatal and postnatal growth, microcephaly, prominent nose with absent glabellar angle, micrognathia, joint abnormalities including flexion contractures, camptodactyly, rocker-bottom feet, and severe psychomotor delay. Most patients do not survive beyond the first year of life as a result of complications associated with reduced mobility and failure to thrive (summary by Armistead et al., 2009).

Microcephalic osteodysplastic primordial dwarfism type I (MOPD1) is a severe autosomal recessive skeletal dysplasia characterized by dwarfism, microcephaly, and neurologic abnormalities, including mental retardation, brain malformations, and ocular/auditory sensory deficits. Patients often die in early childhood (summary by Pierce and Morse, 2012).

Any arthrogryposis-renal dysfunction-cholestasis syndrome in which the cause of the disease is a mutation in the VPS33B gene.

Arterial tortuosity syndrome (ATS) is characterized by widespread elongation and tortuosity of the aorta and mid-sized arteries as well as focal stenosis of segments of the pulmonary arteries and/or aorta combined with findings of a generalized connective tissue disorder, which may include soft or doughy hyperextensible skin, joint hypermobility, inguinal hernia, and diaphragmatic hernia. Skeletal findings include pectus excavatum or carinatum, arachnodactyly, scoliosis, knee/elbow contractures, and camptodactyly. The cardiovascular system is the major source of morbidity and mortality with increased risk at any age for aneurysm formation and dissection both at the aortic root and throughout the arterial tree, and for ischemic vascular events involving cerebrovascular circulation (resulting in non-hemorrhagic stroke) and the abdominal arteries (resulting in infarctions of abdominal organs).

A multiple malformation syndrome in which mandibulofacial dysostosis and severe limb reduction defects are associated with complex malformations of different organs and systems especially the central nervous system, urogenital tract, heart, and lungs. The mandibulofacial defect causes death by respiratory distress. Limb reduction is severe and includes shoulder and pelvis hypoplasia, phocomelia with humerus hypoplasia, absent radius and ulna, complete absence of long bones of the legs, and various hand anomalies, predominantly preaxial reduction. These infants also show facial dysmorphism and ear anomalies. The condition is a rare with an autosomal recessive mode of inheritance. The prognosis is poor and this condition leads to death in utero or shortly after birth.

A very rare multiple congenital anomalies syndrome with characteristics of limb deficiencies and renal anomalies that include split hand-split foot malformation, renal agenesis, polycystic kidneys, uterine anomalies and severe mandibular hypoplasia.

Campomelic dysplasia (CD) is a skeletal dysplasia characterized by distinctive facies, Pierre Robin sequence with cleft palate, shortening and bowing of long bones, and clubfeet. Other findings include laryngotracheomalacia with respiratory compromise and ambiguous genitalia or normal female external genitalia in most individuals with a 46,XY karyotype. Many affected infants die in the neonatal period; additional findings identified in long-term survivors include short stature, cervical spine instability with cord compression, progressive scoliosis, and hearing impairment.

Hypoglossia-hypodactyly syndrome is characterized by a hypoplastic mandible, absence of the lower incisors, hypoglossia, and a variable degree of absence of the digits and limbs. Intelligence is normal (Hall, 1971). Hall (1971) classified what he termed the 'syndromes of oromandibular and limb hypogenesis,' which comprised a range of disorders with hypoglossia in common. Type I included hypoglossia and aglossia in isolation. Type II included hypoglossia with hypomelia/hypodactylia. Type III included glossopalatine ankylosis with hypoglossia or hypoglossia and hypomelia/hypodactyly. Type IV included intraoral bands with fusion with hypoglossia or hypoglossia and hypomelia/hypodactyly. Type V included several syndromes, such as Hanhart syndrome, Pierre Robin syndrome (261800), Moebius syndrome (157900), and amniotic band syndrome (217100). Hall (1971) noted that complete aglossia or adactylia had not been reported, and suggested that 'hypoglossia-hypodactylia' is a more accurate term. See also hypoglossia and situs inversus (612776).

KAT6B disorders include genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) which are part of a broad phenotypic spectrum with variable expressivity; individuals presenting with a phenotype intermediate between GPS and SBBYSS have been reported. Both phenotypes are characterized by some degree of global developmental delay / intellectual disability; hypotonia; genital abnormalities; and skeletal abnormalities including patellar hypoplasia/agenesis, flexion contractures of the knees and/or hips, and anomalies of the digits, spine, and/or ribs. Congenital heart defects, small bowel malrotation, feeding difficulties, slow growth, cleft palate, hearing loss, and dental anomalies have been observed in individuals with either phenotype.

Chromosome 16p13.3deletion syndrome is a chromosome abnormality that can affect many parts of the body. People with this condition are missing a small piece (deletion) of chromosome 16 at a location designated p13.3. Although once thought to be a severe form of Rubinstein-Taybi syndrome, it is now emerging as a unique syndrome. Signs and symptoms may include failure to thrive, hypotonia (reduced muscle tone), short stature, microcephaly (unusually small head), characteristic facial features, mild to moderate intellectual disability, organ anomalies (i.e. heart and/or kidney problems), and vulnerability to infections. Chromosome testing of both parents can provide information about whether the deletion was inherited. In most cases, parents do not have any chromosome abnormalities. However, sometimes one parent has a balanced translocation where a piece of a chromosome has broken off and attached to another one with no gain or loss of genetic material. The balanced translocation normally does not cause signs or symptoms, but it increases the risk for having a child with a chromosome abnormality like a deletion. Treatment is based on the signs and symptoms present in each person.To learn more about chromosome abnormalities in general, view our GARD fact sheet on Chromosome Disorders.

Mandibulofacial dysostosis with microcephaly (MFDM) is characterized by malar and mandibular hypoplasia, microcephaly (congenital or postnatal onset), intellectual disability (mild, moderate, or severe), malformations of the external ear, and hearing loss that is typically conductive. Associated craniofacial malformations may include cleft palate, choanal atresia, zygomatic arch cleft (identified on cranial CT scan), and facial asymmetry. Other relatively common findings (present in 25%-35% of individuals) can include cardiac anomalies, thumb anomalies, esophageal atresia/tracheoesophageal fistula, short stature, spine anomalies, and epilepsy.

This syndrome has characteristics of anophthalmia or microphthalmia, retinal dystrophy, and/or myopia, associated in some cases with cerebral anomalies. It has been described in two families. Polydactyly may also be present. Linkage analysis allowed identification of mutations in the BMP4 gene, which has already been shown to play a role in eye development.

Frias syndrome is characterized by mild exophthalmia, palpebral ptosis, hypertelorism, short square hands with minimal proximal syndactyly between the second and third fingers, small broad great toes, and short stature. Some patients may exhibit bilateral pedunculated postminimi (summary by Martinez-Fernandez et al., 2014).

Mandibulofacial dysostosis-macroblepharon-macrostomia syndrome is a rare developmental defect during embryogenesis disorder characterized by macroblepharon, ectropion, and facial dysmorphism which includes severe hypertelorism, downslanting palpebral fissures, posteriorly rotated ears, broad nasal bridge, long and smooth philtrum, and macrostomia with thin upper lip vermilion border. Other features may include large fontanelles, prominent metopic ridge, thick eyebrows, mild synophrys, increased density of upper eyelashes, anterverted nares, abnormal dentition and capillary hemangioma.

Short stature, auditory canal atresia, mandibular hypoplasia, and skeletal abnormalities (SAMS) is an autosomal recessive multiple congenital anomaly syndrome with features of a first and second branchial arch syndrome. Craniofacial abnormalities can lead to conductive hearing loss, respiratory insufficiency, and feeding difficulties. Additional features include rhizomelic skeletal anomalies as well as abnormalities of the shoulder and pelvic joints. Affected individuals may also have some features of a neurocristopathy or abnormal mesoderm development, such as urogenital anomalies, that are distinct from other branchial arch syndromes (summary by Parry et al., 2013).

Desmosterolosis is a rare autosomal recessive disorder characterized by multiple congenital anomalies and elevated levels of the cholesterol precursor desmosterol in plasma, tissue, and cultured cells (summary by Waterham et al., 2001).

Penttinen syndrome (PENTT) is characterized by a prematurely aged appearance involving lipoatrophy and epidermal and dermal atrophy, as well as hypertrophic lesions that resemble scars, thin hair, proptosis, underdeveloped cheekbones, and marked acroosteolysis (Johnston et al., 2015).

Spondylospinal thoracic dysostosis is an extremely rare skeletal disorder characterized bya short, curved spine and fusion of the spinous processes, short thorax with 'crab-like' configuration of the ribs, underdevelopment of the lungs (pulmonary hypoplasia), severe arthrogryposis and multiple pterygia (webbing of the skin across joints), and underdevelopment of the bones of the mouth.This condition is believed to be inherited in an autosomal recessive manner.It does notappear to be compatible with life.

Splenogonadal fusion (SGF) is a rare congenital anomaly of abnormal fusion between the spleen and the gonad or the remnants of the mesonephros. In 'continuous SGF,' there is a cord-like connection between the 2 organs, whereas in 'discontinuous SGF,' there is fusion of accessory splenic tissue and the gonad without a distinct structural connection to the spleen itself. Forty-eight percent of individuals with continuous SGF have additional malformations, compared to 9% of those with discontinuous SGF (McPherson et al., 2003).

A rare genetic syndrome with characteristics of cleft palate, large protruding ears, microcephaly and short stature (prenatal onset). Other skeletal abnormalities (delayed bone age, distally tapering fingers, hypoplastic distal phalanges, proximally placed thumbs, fifth finger clinodactyly), Pierre Robin sequence, cystic renal dysplasia, proximal renal tubular acidosis, hypospadia, cerebral anomalies on imaging (enlargement of lateral ventricles, mild cortical atrophy), seizures, hypotonia and developmental delay are also observed.

Robin sequence-oligodactyly syndrome is a rare, genetic, developmental defect during embryogenesis syndrome characterized by Robin sequence (i.e. severe micrognathia, retroglossia and U-shaped cleft of the posterior palate) associated with pre- and postaxial oligodactyly. Facial features can include a narrow face and narrow lower dental arch. Clinodactyly, absent phalanx, metacarpal fusions, and hypoplastic carpals have also been reported. There have been no further descriptions in the literature since 1986.

Paris-Trousseau thrombocytopenia (TCPT) is a contiguous gene syndrome characterized by mild bleeding tendency, variable thrombocytopenia (THC), dysmorphic facies, abnormal giant alpha-granules in platelets and dysmegakaryopoiesis.

Wolf-Hirschhorn syndrome is a congenital malformation syndrome characterized by pre- and postnatal growth deficiency, developmental disability of variable degree, characteristic craniofacial features ('Greek warrior helmet' appearance of the nose, high forehead, prominent glabella, hypertelorism, high-arched eyebrows, protruding eyes, epicanthal folds, short philtrum, distinct mouth with downturned corners, and micrognathia), and a seizure disorder (Battaglia et al., 2008).

Autosomal recessive osteopetrosis-5 (OPTB5) is a form of infantile malignant osteopetrosis, characterized by defective osteoclast function resulting in decreased bone resorption and generalized osteosclerosis. Defective resorption causes development of densely sclerotic fragile bones and progressive obliteration of the marrow spaces and cranial foramina. Marrow obliteration is associated with extramedullary hematopoiesis and hepatosplenomegaly, and results in anemia and thrombocytopenia, whereas nerve entrapment accounts for progressive blindness and hearing loss. Other major manifestations include failure to thrive, pathologic fractures, and increased infection rate. Most affected children succumb to severe bone marrow failure and overwhelming infection in the first few years of life (summary by Quarello et al., 2004).

MBD5 haploinsufficiency is a neurodevelopmental disorder characterized by developmental delay, intellectual disability, severe speech impairment, seizures, sleep disturbances, and abnormal behaviors. Most children lack speech entirely or have single words, short phrases, or short sentences. Seizures are present in more than 80% of children; onset is usually around age two years. Sleep disturbances, present in about 90%, can result in excessive daytime drowsiness. Abnormal behaviors can include autistic-like behaviors (80%) and self-injury and aggression (>60%).

Legius syndrome is characterized by multiple café au lait macules without neurofibromas or other tumor manifestations of neurofibromatosis type 1 (NF1). Additional clinical manifestations reported commonly include intertriginous freckling, lipomas, macrocephaly, and learning disabilities / attention-deficit/hyperactivity disorder (ADHD) / developmental delays. Current knowledge of the natural history of Legius syndrome is based on the clinical manifestations of fewer than 300 individuals with a molecularly confirmed diagnosis; better delineation of the clinical manifestations and natural history of Legius syndrome will likely occur as more affected individuals are identified.

Syndrome with characteristics of severe psychomotor retardation, failure to thrive and intolerance to wheat and dairy products. So far, only two cases have been described. The disease is caused by mutations in the COG8 gene, which encodes a subunit of the COG complex. This complex is involved vesicle transport in the Golgi apparatus.

A rare genetic developmental defect during embryogenesis disorder with characteristics of craniofacial dysmorphism (including brachycephaly, prominent forehead, sparse lateral eyebrows, severe hypertelorism, upslanting palpebral fissures, epicanthal folds, protruding ears, broad nasal bridge, pointed nasal tip, flat philtrum, anteverted nostrils, large mouth, thin upper vermilion border, highly arched palate and mild micrognathia) associated with osteopenia leading to repeated long bone fractures, severe myopia, mild to moderate sensorineural or mixed hearing loss, enamel hypoplasia, sloping shoulders and mild intellectual disability. There is evidence the disease can be caused by homozygous mutation in the IRX5 gene on chromosome 16q11.2.

Stickler syndrome is a connective tissue disorder that can include ocular findings of myopia, cataract, and retinal detachment; hearing loss that is both conductive and sensorineural; midfacial underdevelopment and cleft palate (either alone or as part of the Robin sequence); and mild spondyloepiphyseal dysplasia and/or precocious arthritis. Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity.

GNPTAB-related disorders comprise the phenotypes mucolipidosis II (ML II) and mucolipidosis IIIa/ß (ML IIIa/ß), and phenotypes intermediate between ML II and ML IIIa/ß. ML II is evident at birth and slowly progressive; death most often occurs in early childhood. Orthopedic abnormalities present at birth may include thoracic deformity, kyphosis, clubfeet, deformed long bones, and/or dislocation of the hip(s). Growth often ceases in the second year of life; contractures develop in all large joints. The skin is thickened, facial features are coarse, and gingiva are hypertrophic. All children have cardiac involvement, most commonly thickening and insufficiency of the mitral valve and, less frequently, the aortic valve. Progressive mucosal thickening narrows the airways, and gradual stiffening of the thoracic cage contributes to respiratory insufficiency, the most common cause of death. ML IIIa/ß becomes evident at about age three years with slow growth rate and short stature; joint stiffness and pain initially in the shoulders, hips, and fingers; gradual mild coarsening of facial features; and normal to mildly impaired cognitive development. Pain from osteoporosis becomes more severe during adolescence. Cardiorespiratory complications (restrictive lung disease, thickening and insufficiency of the mitral and aortic valves, left and/or right ventricular hypertrophy) are common causes of death, typically in early to middle adulthood. Phenotypes intermediate between ML II and ML IIIa/ß are characterized by physical growth in infancy that resembles that of ML II and neuromotor and speech development that resemble that of ML IIIa/ß.

Loeys-Dietz syndrome (LDS) is characterized by vascular findings (cerebral, thoracic, and abdominal arterial aneurysms and/or dissections), skeletal manifestations (pectus excavatum or pectus carinatum, scoliosis, joint laxity, arachnodactyly, talipes equinovarus, cervical spine malformation and/or instability), craniofacial features (widely spaced eyes, strabismus, bifid uvula / cleft palate, and craniosynostosis that can involve any sutures), and cutaneous findings (velvety and translucent skin, easy bruising, and dystrophic scars). Individuals with LDS are predisposed to widespread and aggressive arterial aneurysms and pregnancy-related complications including uterine rupture and death. Individuals with LDS can show a strong predisposition for allergic/inflammatory disease including asthma, eczema, and reactions to food or environmental allergens. There is also an increased incidence of gastrointestinal inflammation including eosinophilic esophagitis and gastritis or inflammatory bowel disease. Wide variation in the distribution and severity of clinical features can be seen in individuals with LDS, even among affected individuals within a family who have the same pathogenic variant.

Multicentric carpotarsal osteolysis syndrome is a rare skeletal disorder, usually presenting in early childhood with a clinical picture mimicking juvenile rheumatoid arthritis. Progressive destruction of the carpal and tarsal bone usually occurs and other bones may also be involved. Chronic renal failure is a frequent component of the syndrome. Mental retardation and minor facial anomalies have been noted in some patients. Autosomal dominant inheritance has been documented in many families (Pai and Macpherson, 1988). See also Torg-Winchester syndrome (259600), an autosomal recessive multicentric osteolysis syndrome.

10q26 deletion syndrome is a condition that results from the loss (deletion) of a small piece of chromosome 10 in each cell. The deletion occurs on the long (q) arm of the chromosome at a position designated 10q26.\n\nThe signs and symptoms of 10q26 deletion syndrome vary widely, even among affected members of the same family. Among the more common features associated with this chromosomal change are distinctive facial features, mild to moderate intellectual disability, growth problems, and developmental delay. People with 10q26 deletion syndrome often have delayed development of speech and of motor skills such as sitting, crawling, and walking. Some have limited speech throughout life. Affected individuals may experience seizures, attention-deficit/hyperactivity disorder (ADHD), poor impulse control (impulsivity), or exhibit autistic behaviors that affect communication and social interaction.\n\nA range of facial features is seen in people with 10q26 deletion syndrome, but not all affected individuals have these features. Facial features of people with 10q26 deletion syndrome may include a prominent or beaked nose, a broad nasal bridge, a small jaw (micrognathia), malformed ears that are low set, a thin upper lip, and an unusually small head size (microcephaly). Many affected individuals have widely spaced eyes (hypertelorism) that do not look in the same direction (strabismus). Some people with this condition have a short neck with extra folds of skin (webbed neck).\n\nLess common signs and symptoms can occur in 10q26 deletion syndrome. Skeletal problems include a spine that curves to the side (scoliosis), limited movement in the elbows or other joints, or curved fifth fingers and toes (clinodactyly). Slow growth before and after birth can also occur in affected individuals. Males with this condition may have genital abnormalities, such as a small penis (micropenis), undescended testes (cryptorchidism), or the urethra opening on the underside of the penis (hypospadias). Some people with 10q26 deletion syndrome have kidney abnormalities, heart defects, breathing problems, recurrent infections, or hearing or vision problems.

Endocrine-cerebro-osteodysplasia (ECO) syndrome is characterized by various anomalies of the endocrine, cerebral, and skeletal systems resulting in neonatal mortality.

22q11.2 duplication is a condition caused by an extra copy of a small piece of chromosome 22. The duplication occurs near the middle of the chromosome at a location designated q11.2.\n\nThe features of this condition vary widely, even among members of the same family. Affected individuals may have developmental delay, intellectual disability, slow growth leading to short stature, and weak muscle tone (hypotonia). Many people with the duplication have no apparent physical or intellectual disabilities.

Distal monosomy 15q is a rare chromosomal anomaly syndrome characterized by pre- and postnatal growth restriction, developmental delay, variable degrees of intellectual disability, hand and foot anomalies (e.g. brachy-/clinodactyly, talipes equinovarus, nail hypoplasia, proximally placed digits) and mild craniofacial dysmorphism (incl. microcephaly, triangular face, broad nasal bridge, micrognathia). Neonatal lymphedema, heart malformations, aplasia cutis congenita, aortic root dilatation, and autistic spectrum disorder have also been reported.

The 1q21.1 recurrent microdeletion itself does not appear to lead to a clinically recognizable syndrome as some persons with the deletion have no obvious clinical findings and others have variable findings that most commonly include microcephaly (50%), mild intellectual disability (30%), mildly dysmorphic facial features, and eye abnormalities (26%). Other findings can include cardiac defects, genitourinary anomalies, skeletal malformations, and seizures (~15%). Psychiatric and behavioral abnormalities can include autism spectrum disorders, attention deficit hyperactivity disorder, autistic features, and sleep disturbances.

For a detailed discussion of the WAGR syndrome, see 194072. In a subgroup of individuals with the WAGR syndrome, obesity develops. The phenotype in this subset is associated with haploinsufficiency for the BDNF gene.

Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia or no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

SATB2-associated syndrome (SAS) is a multisystem disorder characterized by significant neurodevelopmental compromise with limited to absent speech, behavioral issues, and craniofacial anomalies. All individuals described to date have manifest developmental delay / intellectual disability, with severe speech delay. Affected individuals often have hypotonia and feeding difficulties in infancy. Behavioral issues may include autistic features, hyperactivity, and aggressiveness. Craniofacial anomalies may include palatal abnormalities (cleft palate, high-arched palate, and bifid uvula), micrognathia, and abnormal shape or size of the upper central incisors. Less common features include skeletal anomalies (osteopenia, pectus deformities, kyphosis/lordosis, and scoliosis), growth restriction, strabismus/refractive errors, congenital heart defects, genitourinary anomalies, and epilepsy. While dysmorphic features have been described in individuals with this condition, these features are not typically distinctive enough to allow for a clinical diagnosis of SAS.

SLC25A24 Fontaine progeroid syndrome is a multisystem connective tissue disorder characterized by poor growth, abnormal skeletal features, and distinctive craniofacial features with sagging, thin skin, and decreased subcutaneous fat suggesting an aged appearance that is most pronounced in infancy and improves with time. Characteristic radiographic features include turribrachycephaly with widely open anterior fontanelle, craniosynostosis, and anomalies of the terminal phalanges. Cardiovascular, genitourinary, ocular, and gastrointestinal abnormalities may also occur. To date, 13 individuals with a molecularly confirmed diagnosis of SLC25A24 Fontaine progeroid syndrome have been described.

Congenital disorders of glycosylation (CDGs) are a genetically heterogeneous group of autosomal recessive disorders caused by enzymatic defects in the synthesis and processing of asparagine (N)-linked glycans or oligosaccharides on glycoproteins. Type I CDGs comprise defects in the assembly of the dolichol lipid-linked oligosaccharide (LLO) chain and its transfer to the nascent protein. These disorders can be identified by a characteristic abnormal isoelectric focusing profile of plasma transferrin (Leroy, 2006). For a discussion of the classification of CDGs, see CDG1A (212065).

CASK disorders include a spectrum of phenotypes in both females and males. Two main types of clinical presentation are seen: Microcephaly with pontine and cerebellar hypoplasia (MICPCH), generally associated with pathogenic loss-of-function variants in CASK. X-linked intellectual disability (XLID) with or without nystagmus, generally associated with hypomorphic CASK pathogenic variants. MICPCH is typically seen in females with moderate-to-severe intellectual disability, progressive microcephaly with or without ophthalmologic anomalies, and sensorineural hearing loss. Most are able to sit independently; 20%-25% attain the ability to walk; language is nearly absent in most. Neurologic features may include axial hypotonia, hypertonia/spasticity of the extremities, and dystonia or other movement disorders. Nearly 40% have seizures by age ten years. Behaviors may include sleep disturbances, hand stereotypies, and self biting. MICPCH in males may occur with or without severe epileptic encephalopathy in addition to severe-to-profound developmental delay. When seizures are present they occur early and may be intractable. In individuals and families with milder (i.e., hypomorphic) pathogenic variants, the clinical phenotype is usually that of XLID with or without nystagmus and additional clinical features. Males have mild-to-severe intellectual disability, with or without nystagmus and other ocular features. Females typically have normal intelligence with some displaying mild-to-severe intellectual disability with or without ocular features.

X-linked intellectual disability-craniofacioskeletal syndrome is a rare, hereditary, syndromic intellectual disability characterized by craniofacial and skeletal abnormalities in association with mild intellectual disability in females and early postnatal lethality in males. In addition to mild cognitive impairment, females present with microcephaly, short stature, skeletal features and extra temporal lobe gyrus. In males, intrauterine growth impairment, cardiac and urogenital anomalies have been reported.

Turner-type X-linked syndromic intellectual developmental disorder (MRXST) is a neurodevelopmental disorder with a highly variable phenotype. Some affected families show X-linked recessive inheritance, with only males being affected and carrier females having no abnormal findings. In other affected families, males are severely affected, and female mutation carriers show milder cognitive abnormalities or dysmorphic features. In addition, there are female patients with de novo mutations who show the full phenotype, despite skewed X-chromosome inactivation. Affected individuals show global developmental delay from infancy, with variably impaired intellectual development and poor or absent speech, often with delayed walking. Dysmorphic features are common and can include macrocephaly, microcephaly, deep-set eyes, hypotelorism, small palpebral fissures, dysplastic, large, or low-set ears, long face, bitemporal narrowing, high-arched palate, thin upper lip, and scoliosis or mild distal skeletal anomalies, such as brachydactyly or tapered fingers. Males tend to have cryptorchidism. Other features, such as hypotonia, seizures, and delayed bone age, are more variable (summary by Moortgat et al., 2018).

Dermatosparaxis (meaning 'tearing of skin') is an autosomal recessive disorder of connective tissue resulting from deficiency of procollagen peptidase, an enzyme that aids in the processing of type I procollagen. The disorder and the responsible biochemical defect was first observed in cattle (Lapiere et al., 1971). Lapiere and Nusgens (1993) reviewed the discovery of dermatosparaxis in cattle, the elucidation of the disorder, its occurrence in other animals, and the delayed recognition of the disorder in the human.

Orofaciodigital syndrome type VI (OFD6), or Varadi syndrome, is a rare autosomal recessive disorder distinguished from other orofaciodigital syndromes by metacarpal abnormalities with central polydactyly and by cerebellar abnormalities, including the molar tooth sign (summary by Doss et al., 1998 and Lopez et al., 2014).

Hypoglossia with situs inversus is a very rare congenital condition that likely represents a developmental field defect. Only sporadic cases have been reported (Faqeih et al., 2008). Hypoglossia is part of a group of malformation syndromes collectively termed 'oromandibular limb hypogenesis syndromes,' that usually include limb defects. Hall (1971) provided a classification system (see 103300). See also agnathia with holoprosencephaly (202650), which shows hypoglossia and situs inversus in addition to severe neurodevelopmental defects.

Autosomal recessive form of oculodentodigital dysplasia.

Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia or no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

Omodysplasia-2 (OMOD2) is a rare autosomal dominant skeletal dysplasia characterized by shortened humeri, dislocated radial heads, shortened first metacarpals, craniofacial dysmorphism, and variable genitourinary anomalies (Saal et al., 2015). For a discussion of genetic heterogeneity of OMOD, see 258315.

LTBP4-related cutis laxa is characterized by cutis laxa, early childhood-onset pulmonary emphysema, peripheral pulmonary artery stenosis, and other evidence of a generalized connective tissue disorder such as inguinal hernias and hollow visceral diverticula (e.g., intestine, bladder). Other manifestations can include pyloric stenosis, diaphragmatic hernia, rectal prolapse, gastrointestinal elongation/tortuosity, cardiovascular abnormality, pulmonary hypertension, hypotonia and frequent pulmonary infections. Bladder diverticula and hydronephrosis are common. Early demise has been associated with pulmonary emphysema.

A very rare inherited connective tissue disorder with characteristics of macrocephaly, sparse scalp hair, soft redundant and hyperextensible skin, joint hypermobility, and scoliosis. Patients have progressive facial coarsening with downslanted palpebral fissures, upper eyelid fullness/infraorbital folds, thick/everted vermillion, gingival overgrowth and abnormal position of the teeth. Rare manifestations such as abnormal high-pitched voice, bronchiectasis, hypergonadotropic hypergonadism and brachydactyly have also been reported. Caused by homozygous mutation in the RIN2 gene on chromosome 20p11.

Congenital disorder of glycosylation type It (CDG1T) is an autosomal recessive disorder characterized by a wide range of clinical manifestations and severity. The most common features include cleft lip and bifid uvula, apparent at birth, followed by hepatopathy, intermittent hypoglycemia, short stature, and exercise intolerance, often accompanied by increased serum creatine kinase. Less common features include rhabdomyolysis, dilated cardiomyopathy, and hypogonadotropic hypogonadism (summary by Tegtmeyer et al., 2014). For a discussion of the classification of CDGs, see CDG1A (212065).

Sex reversal in an individual associated with a 9p24.3 deletion.

Like all CDGs, which are caused by a shortage of precursor monosaccharide phosphate or deficiencies in the glycosyltransferases required for lipid-linked oligosaccharide precursor (LLO) synthesis, CDG Ij is caused by a defect in the formation of DPAGT1, the first dolichyl-linked intermediate of the protein N-glycosylation pathway. For a general discussion of CDGs, see CDG1A (212065).

Congenital disorders of glycosylation (CDGs) comprise a group of multisystem diseases with mostly severe psychomotor and mental retardation. Type I CDG comprises those disorders in which there are defects that affect biosynthesis of dolichol-linked oligosaccharides in the cytosol or the endoplasmic reticulum (ER), as well as defects involving the transfer of oligosaccharides onto nascent glycoproteins. Type II CDG comprises all defects of further trimming and elongation of N-linked oligosaccharides in the ER and Golgi (Schwarz et al., 2004). CDG1K is a type I CDG characterized by predominant neurologic involvement. Survival ranges from the second day of life to adulthood. The liver is affected in a minority of patients and shows hepatomegaly, edema, ascites, cholestatic jaundice, portal hypertension, and Budd-Chiari syndrome (summary by Marques-da-Silva et al., 2017). For a general discussion of CDGs, see CDG1A (212065).

CDG IIe is caused by a mutation that impairs the integrity of the conserved oligomeric Golgi (COG) complex and alters Golgi trafficking, resulting in the disruption of multiple glycosylation pathways. For a general discussion of CDGs, see CDG1A (212065).

An extremely rare form of carbohydrate deficient glycoprotein syndrome with, in the few cases reported to date, variable signs including microcephaly, growth retardation, psychomotor retardation and facial dysmorphism.

Greenberg dysplasia (GRBGD), also known as hydrops-ectopic calcification-moth-eaten (HEM) skeletal dysplasia, is a rare autosomal recessive osteochondrodysplasia characterized by gross fetal hydrops, severe shortening of all long bones with a moth-eaten radiographic appearance, platyspondyly, disorganization of chondroosseous calcification, and ectopic ossification centers. It is lethal in utero. Patient fibroblasts show increased levels of cholesta-8,14-dien-3-beta-ol, suggesting a defect of sterol metabolism (summary by Konstantinidou et al., 2008). Herman (2003) reviewed the cholesterol biosynthetic pathway and 6 disorders involving enzyme defects in postsqualene cholesterol biosynthesis: Smith-Lemli-Opitz syndrome (SLOS; 270400), desmosterolosis (602398), X-linked dominant chondrodysplasia punctata (CDPX2; 302960), CHILD syndrome (308050), lathosterolosis (607330), and HEM skeletal dysplasia.

The association of Pierre Robin sequence (retrognathia, cleft palate and glossoptosis), facial dysmorphism (high forehead with frontal bossing) and digital anomalies (tapering fingers, hyper convex nails, clinodactyly of the fifth fingers and short distal phalanges, finger-like thumbs and easily subluxated first metacarpophalangeal joints). Growth and mental development are normal. It has been described in two half brothers born to the same mother. Transmission appears to be X-linked recessive.

Potocki-Lupski syndrome (PTLS) is characterized by cognitive, behavioral, and medical manifestations. Cognitively, most individuals present with developmental delay, later meeting criteria for moderate intellectual disability. Behaviorally, issues with attention, hyperactivity, withdrawal, and anxiety may be seen. Some individuals meet criteria for autism spectrum disorder. Medically, hypotonia, oropharyngeal dysphagia leading to failure to thrive, congenital heart disease, hypoglycemia associated with growth hormone deficiency, and mildly dysmorphic facial features are observed. Medical manifestations typically lead to identification of PTLS in infancy; however, those with only behavioral and cognitive manifestations may be identified in later childhood.

Zlotogora-Ogur syndrome is an ectodermal dysplasia syndrome with characteristics of hair, skin and teeth anomalies, facial dysmorphism with cleft lip and palate, cutaneous syndactyly and, in some cases, intellectual disability.The prevalence is unknown but to date, less than 50 cases have been described in the literature. Caused by mutations in the gene PVRL1 (11q23-q24) which encodes nectin-1, the principal receptor used by alpha-herpesviruses to mediate entry into human cells. Transmission is autosomal recessive.

The Catania type of acrofacial dysostosis is characterized by intrauterine growth retardation, short stature, microcephaly, intellectual disability, widow's peak, mandibulofacial dysostosis without cleft palate, ear anomalies, mild pre- and postaxial limb hypoplasia with brachydactyly, mild interdigital webbing, dental anomalies, and cryptorchidism and hypospadias in males (Opitz et al., 1993; Wulfsberg et al., 1996).

Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia or no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

Congenital alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is characterized histologically by failure of formation and ingrowth of alveolar capillaries that then do not make contact with alveolar epithelium, medial muscular thickening of small pulmonary arterioles with muscularization of the intraacinar arterioles, thickened alveolar walls, and anomalously situated pulmonary veins running alongside pulmonary arterioles and sharing the same adventitial sheath. Less common features include a reduced number of alveoli and a patchy distribution of the histopathologic changes. The disorder is associated with persistent pulmonary hypertension of the neonate and shows varying degrees of lability and severity (Boggs et al., 1994). Affected infants present with respiratory distress resulting from pulmonary hypertension in the early postnatal period, and the disease is uniformly fatal within the newborn period (Vassal et al., 1998). Additional features of ACDMPV include multiple congenital anomalies affecting the cardiovascular, gastrointestinal, genitourinary, and musculoskeletal systems, as well as disruption of the normal right-left asymmetry of intrathoracic or intraabdominal organs (Sen et al., 2004).

The 16p11.2 recurrent deletion phenotype is characterized by motor speech disorder, language disorder, motor coordination difficulties, psychiatric conditions, and autistic features. While most, if not all, individuals with the 16p11.2 recurrent deletion experience some degree of developmental delay, the severity varies significantly. Most affected individuals do not have intellectual disability (defined as an IQ of <70), but many have below average cognition and learning disabilities in both verbal and nonverbal domains. Obesity is a feature of this disorder and generally emerges in childhood; BMI in individuals with the 16p11.2 recurrent deletion is significantly higher than in the general population by age five years. Seizures are observed in approximately 25% of individuals with the recurrent deletion. Vertebral anomalies, hearing impairment, macrocephaly, and cardiovascular malformation have each been observed in some individuals. Clinical follow-up data from adults suggests that the greatest medical challenges are obesity and related comorbidities that can be exacerbated by medications used to treat behavioral and psychiatric problems.

14q11.2 microdeletion syndrome is a recently described syndrome characterized by developmental delay, hypotonia and facial dysmorphism.

16p13.3 microduplication syndrome is a rare chromosomal anomaly syndrome resulting from a partial duplication of the short arm of chromosome 16 and manifesting with a variable phenotype which is mostly characterized by: mild to moderate intellectual deficit and developmental delay (particularly speech), normal growth, short, proximally implanted thumbs and other hand and feet malformations (such as camptodactyly, syndactyly, club feet), mild arthrogryposis and characteristic facies (upslanting, narrow palpebral fissures, hypertelorism, mid face hypoplasia, bulbous nasal tip and low set ears). Other reported manifestations include cryptorchidism, inguinal hernia and behavioral problems.

The cardinal features of chromosome 6q11-q14 interstitial deletions include hypotonia, short stature, skeletal/limb anomalies, umbilical hernia, and urinary tract anomalies, as well as characteristic facial features including upslanting palpebral fissures, low-set and/or dysplastic ears, and high-arched palate (summary by Wang et al., 2009).

The chromosome 16p12.2-p11.2 deletion syndrome is characterized phenotypically by dysmorphic facial features, feeding difficulties, recurrent ear infections, developmental delay, and cognitive impairment. Additional features, such as heart defects and short stature, are variable (Ballif et al., 2007; Battaglia et al., 2009). The pericentric region of chromosome 16, specifically involving 16p12-p11, is a structurally complex region enriched in repetitive sequence elements, rendering this region susceptible to deletion or rearrangement (Ballif et al., 2007). There are several phenotypes associated with variation in this region: see 611913 for a deletion or duplication at 16p11.2 associated with autism; see 136570 for discussion of a recurrent 520-kb deletion at 16p12.1 associated with developmental delay and craniofacial dysmorphism; and see 613444 for a 220-kb deletion at 16p11.2 associated with isolated severe early-onset obesity and obesity with developmental delay. Battaglia et al. (2009) emphasized that the region at chromosome 16p11.2 that confers susceptibility to autism (AUTS14; see 611913) is located more centromeric to and is distinct from the 16p12.2-p11.2 region involved in the multiple congenital anomalies and intellectual disability phenotype.

Cranioectodermal dysplasia (CED) is a ciliopathy with skeletal involvement (narrow thorax, shortened proximal limbs, syndactyly, polydactyly, brachydactyly), ectodermal features (widely spaced hypoplastic teeth, hypodontia, sparse hair, skin laxity, abnormal nails), joint laxity, growth deficiency, and characteristic facial features (frontal bossing, low-set simple ears, high forehead, telecanthus, epicanthal folds, full cheeks, everted lower lip). Most affected children develop nephronophthisis that often leads to end-stage kidney disease in infancy or childhood, a major cause of morbidity and mortality. Hepatic fibrosis and retinal dystrophy are also observed. Dolichocephaly, often secondary to sagittal craniosynostosis, is a primary manifestation that distinguishes CED from most other ciliopathies. Brain malformations and developmental delay may also occur.

THOC6 intellectual disability syndrome is associated with moderate-to-severe developmental delay or intellectual disability; nonspecific dysmorphic facial features (tall forehead, deep-set eyes, short and upslanted palpebral fissures, epicanthal folds, and long nose with low-hanging columella); microcephaly (typically 2-3 SD below the mean); teeth anomalies (dental caries, malocclusion, and supernumerary teeth); cardiac anomalies (most typically atrial and/or ventricular septal defects); prenatal ventriculomegaly and hydrocephalus; cryptorchidism in males; and renal malformations (most commonly unilateral renal agenesis). More rarely, affected individuals may have hypergonadotropic hypogonadism (in females), seizures, poor growth, feeding difficulties, hearing loss, refractive errors and/or other eye abnormalities, vertebral anomalies, micro/retrognathia, and imperforate / anteriorly placed anus.

Rubinstein-Taybi syndrome (RSTS) is characterized by distinctive facial features, broad and often angulated thumbs and halluces, short stature, and moderate-to-severe intellectual disability. The characteristic craniofacial features are downslanted palpebral fissures, low-hanging columella, high palate, grimacing smile, and talon cusps. Prenatal growth is often normal, then height, weight, and head circumference percentiles rapidly drop in the first few months of life. Short stature is typical in adulthood. Obesity may develop in childhood or adolescence. Average IQ ranges between 35 and 50; however, developmental outcome varies considerably. Some individuals with EP300-RSTS have normal intellect. Additional features include ocular abnormalities, hearing loss, respiratory difficulties, congenital heart defects, renal abnormalities, cryptorchidism, feeding problems, recurrent infections, and severe constipation.

Treacher Collins syndrome (TCS) is characterized by bilateral and symmetric downslanting palpebral fissures, malar hypoplasia, micrognathia, and external ear abnormalities. Hypoplasia of the zygomatic bones and mandible can cause significant feeding and respiratory difficulties. About 40%-50% of individuals have conductive hearing loss attributed most commonly to malformation of the ossicles and hypoplasia of the middle ear cavities. Inner ear structures tend to be normal. Other, less common abnormalities include cleft palate and unilateral or bilateral choanal stenosis or atresia. Typically intellect is normal.

Meier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.\n\nAdditional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nSome people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).

Some people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nAdditional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.\n\nMeier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.

Meier-Gorlin syndrome-4 (MGORS4) is a rare autosomal recessive disorder with the hallmarks of short stature, small external ears, and reduced or absent patellae. Breast hypoplasia is present in females (Guernsey et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of Meier-Gorlin syndrome, see 224690.

Some people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nAdditional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.\n\nMeier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.

Seckel syndrome is an autosomal recessive disorder characterized by proportionate short stature, severe microcephaly, mental retardation, and a typical 'bird-head' facial appearance (summary by Kalay et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of Seckel syndrome, see 210600.

Osteogenesis imperfecta (OI) comprises a group of connective tissue disorders characterized by bone fragility and low bone mass. The disorder is clinically and genetically heterogeneous. OI type X is an autosomal recessive form characterized by multiple bone deformities and fractures, generalized osteopenia, dentinogenesis imperfecta, and blue sclera (Christiansen et al., 2010).

The chromosome 13q14 deletion syndrome is characterized by retinoblastoma (180200), variable degrees of mental impairment, and characteristic facial features, including high forehead, prominent philtrum, and anteverted earlobes (summary by Caselli et al., 2007).

Osteogenesis imperfecta (OI) comprises a group of connective tissue disorders characterized by bone fragility and low bone mass. The disorder is clinically and genetically heterogeneous. OI type XII is an autosomal recessive form characterized by recurrent fractures, mild bone deformations, generalized osteoporosis, delayed teeth eruption, progressive hearing loss, no dentinogenesis imperfecta, and white sclerae (summary by Lapunzina et al., 2010).

Nestor-Guillermo progeria syndrome (NGPS) is an autosomal recessive disorder characterized by lipoatrophy, osteoporosis, and very severe osteolysis. Patients have no cardiovascular impairment, diabetes mellitus, or hypertriglyceridemia, but suffer profound skeletal abnormalities that affect their quality of life. Onset is after 2 years of age, and lifespan is relatively long (summary by Cabanillas et al., 2011).

A rare multiple congenital anomalies syndrome characterized by cutaneous mastocytosis, microcephaly, microtia and/or hearing loss, hypotonia and skeletal anomalies (e.g. clinodactyly, camptodactyly, scoliosis). Additional common features are short stature, intellectual disability and difficulties. Facial dysmorphism may include upslanted palpebral fissures, highly arched palate and micrognathia. Rarely, seizures and asymmetrically small feet have been reported.

An autosomal recessive muscular dystrophy caused by mutations in the POMGNT1 gene. It is associated with characteristic brain and eye malformations, profound mental retardation, and death usually in the first years of life.

The NSDHL-related disorders include: CHILD (congenital hemidysplasia with ichthyosiform nevus and limb defects) syndrome, an X-linked condition that is usually male lethal during gestation and thus predominantly affects females; and CK syndrome, an X-linked disorder that affects males. CHILD syndrome is characterized by unilateral distribution of ichthyosiform (yellow scaly) skin lesions and ipsilateral limb defects that range from shortening of the metacarpals and phalanges to absence of the entire limb. Intellect is usually normal. The ichthyosiform skin lesions are usually present at birth or in the first weeks of life; new lesions can develop in later life. Nail changes are also common. The heart, lung, and kidneys can also be involved. CK syndrome (named for the initials of the original proband) is characterized by mild to severe cognitive impairment and behavior problems (aggression, attention deficit hyperactivity disorder, and irritability). All affected males reported have developed seizures in infancy and have cerebral cortical malformations and microcephaly. All have distinctive facial features, a thin habitus, and relatively long, thin fingers and toes. Some have scoliosis and kyphosis. Strabismus is common. Optic atrophy is also reported.

D-2-hydroxyglutaric aciduria is a neurometabolic disorder first described by Chalmers et al. (1980). Clinical symptoms include developmental delay, epilepsy, hypotonia, and dysmorphic features. Mild and severe phenotypes were characterized (van der Knaap et al., 1999). The severe phenotype is homogeneous and is characterized by early infantile-onset epileptic encephalopathy and, often, cardiomyopathy. The mild phenotype has a more variable clinical presentation. Genetic Heterogeneity of D-2-Hydroxyglutaric Aciduria D-2-hydroxyglutaric aciduria-2 (D2HGA2; 613657) is caused by heterozygous mutation in the mitochondrial isocitrate dehydrogenase-2 gene (IDH2; 147650) on chromosome 15q26.

A heterozygous deletion of chromosome 15q11.2 may increase the susceptibility to neuropsychiatric or neurodevelopmental problems, including delayed psychomotor development, speech delay, autism spectrum disorder, attention deficit-hyperactivity disorder, obsessive-compulsive disorder, and possibly seizures (summary by Doornbos et al., 2009 and Burnside et al., 2011). See also chromosome 15q11.2 duplication syndrome (608636).

Ogden syndrome (OGDNS) is an X-linked neurodevelopmental disorder characterized by postnatal growth failure, severely delayed psychomotor development, variable dysmorphic features, and hypotonia. Many patients also have cardiac malformations or arrhythmias (summary by Popp et al., 2015).

Kabuki syndrome (KS) is characterized by typical facial features (long palpebral fissures with eversion of the lateral third of the lower eyelid; arched and broad eyebrows; short columella with depressed nasal tip; large, prominent, or cupped ears), minor skeletal anomalies, persistence of fetal fingertip pads, mild-to-moderate intellectual disability, and postnatal growth deficiency. Other findings may include: congenital heart defects, genitourinary anomalies, cleft lip and/or palate, gastrointestinal anomalies including anal atresia, ptosis and strabismus, and widely spaced teeth and hypodontia. Functional differences can include: increased susceptibility to infections and autoimmune disorders, seizures, endocrinologic abnormalities (including isolated premature thelarche in females), feeding problems, and hearing loss.

Multiple congenital anomalies-hypotonia-seizures syndrome-2 (MCAHS2) is an X-linked recessive neurodevelopmental disorder characterized by dysmorphic features, neonatal hypotonia, early-onset myoclonic seizures, and variable congenital anomalies involving the central nervous, cardiac, and urinary systems. Some affected individuals die in infancy (summary by Johnston et al., 2012). The phenotype shows clinical variability with regard to severity and extraneurologic features. However, most patients present in infancy with early-onset epileptic encephalopathy associated with developmental arrest and subsequent severe neurologic disability; these features are consistent with a form of developmental and epileptic encephalopathy (DEE) (summary by Belet et al., 2014, Kato et al., 2014). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of MCAHS, see MCAHS1 (614080). For a discussion of nomenclature and genetic heterogeneity of DEE, see 308350. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).

A distinct group of inborn defects of complex V (ATP synthase) is represented by the enzyme deficiency due to nuclear genome mutations characterized by a selective inhibition of ATP synthase biogenesis. Biochemically, the patients show a generalized decrease in the content of ATP synthase complex which is less than 30% of normal. Most cases present with neonatal-onset hypotonia, lactic acidosis, hyperammonemia, hypertrophic cardiomyopathy, and 3-methylglutaconic aciduria. Many patients die within a few months or years (summary by Mayr et al., 2010). Genetic Heterogeneity of Mitochondrial Complex V Deficiency Other nuclear types of mitochondrial complex V deficiency include MC5DN2 (614052), caused by mutation in the TMEM70 gene (612418) on chromosome 8q21; MC5DN3 (614053), caused by mutation in the ATP5E gene (ATP5F1E; 606153) on chromosome 20q13; MC5DN4A (620358) and MC5DN4B (615228), both caused by mutation in the ATP5A1 gene (ATP5F1A; 164360) on chromosome 18q; MC5DN5 (618120), caused by mutation in the ATP5D gene (ATP5F1D; 603150) on chromosome 19p13; MC5DN6 (618683), caused by mutation in the USMG5 gene (ATP5MD; 615204) on chromosome 10q24; and MC5DN7 (620359), caused by mutation in the ATP5PO gene (600828) on chromosome 21q22. Mutations in the mitochondrial-encoded MTATP6 (516060) and MTATP8 (516070) genes can also cause mitochondrial complex V deficiency (see, e.g., 500015).

CHST3-related skeletal dysplasia is characterized by short stature of prenatal onset, joint dislocations (knees, hips, radial heads), clubfeet, and limitation of range of motion that can involve all large joints. Kyphosis and occasionally scoliosis with slight shortening of the trunk develop in childhood. Minor heart valve dysplasia has been described in several persons. Intellect and vision are normal.

The GPAPP-type of chondrodysplasia with joint dislocations is an autosomal recessive disorder characterized by short stature, chondrodysplasia with brachydactyly, congenital joint dislocations, cleft palate, and facial dysmorphism (Vissers et al., 2011).

Multiple congenital anomalies-hypotonia-seizures syndrome is an autosomal recessive disorder characterized by neonatal hypotonia, lack of psychomotor development, seizures, dysmorphic features, and variable congenital anomalies involving the cardiac, urinary, and gastrointestinal systems. Most affected individuals die before 3 years of age (summary by Maydan et al., 2011). The disorder is caused by a defect in glycosylphosphatidylinositol biosynthesis; see GPIBD1 (610293). Genetic Heterogeneity of Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome MCAHS2 (300868) is caused by mutation in the PIGA gene (311770) on chromosome Xp22, MCAHS3 (615398) is caused by mutation in the PIGT gene (610272) on chromosome 20q13, and MCAHS4 (618548) is caused by mutation in the PIGQ gene (605754) on chromosome 16p13. Knaus et al. (2018) provided a review of the main clinical features of the different types of MCAHS, noting that patients with mutations in the PIGN, PIGA, and PIGT genes have distinct patterns of facial anomalies that can be detected by computer-assisted comparison. Some individuals with MCAHS may have variable increases in alkaline phosphatase (AP) as well as variable decreases in GPI-linked proteins that can be detected by flow cytometry. However, there was no clear correlation between AP levels or GPI-linked protein abnormalities and degree of neurologic involvement, mutation class, or gene involved. Knaus et al. (2018) concluded that a distinction between MCAHS and HPMRS1 (239300), which is also caused by mutation in genes involved in GPI biosynthesis, may be artificial and even inaccurate, and that all these disorders should be considered and classified together under the more encompassing term of 'GPI biosynthesis defects' (GPIBD).

Keppen-Lubinsky syndrome (KPLBS) is a rare disorder characterized by severely delayed psychomotor development, hypertonia, hyperreflexia, generalized lipodystrophy giving an aged appearance, and distinctive dysmorphic features, including microcephaly, prominent eyes, narrow nasal bridge, and open mouth (summary by Masotti et al., 2015).

Cranioectodermal dysplasia (CED) is a ciliopathy with skeletal involvement (narrow thorax, shortened proximal limbs, syndactyly, polydactyly, brachydactyly), ectodermal features (widely spaced hypoplastic teeth, hypodontia, sparse hair, skin laxity, abnormal nails), joint laxity, growth deficiency, and characteristic facial features (frontal bossing, low-set simple ears, high forehead, telecanthus, epicanthal folds, full cheeks, everted lower lip). Most affected children develop nephronophthisis that often leads to end-stage kidney disease in infancy or childhood, a major cause of morbidity and mortality. Hepatic fibrosis and retinal dystrophy are also observed. Dolichocephaly, often secondary to sagittal craniosynostosis, is a primary manifestation that distinguishes CED from most other ciliopathies. Brain malformations and developmental delay may also occur.

Mosaic variegated aneuploidy syndrome is an autosomal recessive disorder characterized by poor growth and variable phenotypic manifestations, such as facial dysmorphism and congenital heart defects, associated with mosaic aneuploidies resulting from defects in cell division (summary by Snape et al., 2011). See also MVA1 (257300), caused by mutation in the BUB1B gene (602860) on chromosome 15q15.

Hydrolethalus syndrome is an autosomal recessive embryonic lethal disorder characterized by hydrocephaly or anencephaly, postaxial polydactyly of the upper limbs, and pre- or postaxial polydactyly of the lower limbs. Duplication of the hallux is a common finding. HLS2 is considered a ciliopathy (summary by Putoux et al., 2011). Acrocallosal syndrome (ACLS; 200990) is an allelic disorder with a less severe phenotype. For a discussion of genetic heterogeneity of hydrolethalus syndrome, see 236680.

Adams-Oliver syndrome (AOS) is characterized by aplasia cutis congenita (ACC) of the scalp and terminal transverse limb defects (TTLD). ACC lesions usually occur in the midline of the parietal or occipital regions, but can also occur on the abdomen or limbs. At birth, an ACC lesion may already have the appearance of a healed scar. ACC lesions less than 5 cm often involve only the skin and almost always heal over a period of months; larger lesions are more likely to involve the skull and possibly the dura, and are at greater risk for complications, which can include infection, hemorrhage, or thrombosis, and can result in death. The limb defects range from mild (unilateral or bilateral short distal phalanges) to severe (complete absence of all toes or fingers, feet or hands, or more, often resembling an amputation). The lower extremities are almost always more severely affected than the upper extremities. Additional major features frequently include cardiovascular malformations/dysfunction (23%), brain anomalies, and less frequently renal, liver, and eye anomalies.

RAB18 deficiency is the molecular deficit underlying both Warburg micro syndrome (characterized by eye, nervous system, and endocrine abnormalities) and Martsolf syndrome (characterized by similar – but milder – findings). To date Warburg micro syndrome comprises >96% of reported individuals with genetically defined RAB18 deficiency. The hallmark ophthalmologic findings are bilateral congenital cataracts, usually accompanied by microphthalmia, microcornea (diameter <10), and small atonic pupils. Poor vision despite early cataract surgery likely results from progressive optic atrophy and cortical visual impairment. Individuals with Warburg micro syndrome have severe to profound intellectual disability (ID); those with Martsolf syndrome have mild to moderate ID. Some individuals with RAB18 deficiency also have epilepsy. In Warburg micro syndrome, a progressive ascending spastic paraplegia typically begins with spastic diplegia and contractures during the first year, followed by upper-limb involvement leading to spastic quadriplegia after about age five years, often eventually causing breathing difficulties. In Martsolf syndrome infantile hypotonia is followed primarily by slowly progressive lower-limb spasticity. Hypogonadism – when present – manifests in both syndromes, in males as micropenis and/or cryptorchidism and in females as hypoplastic labia minora, clitoral hypoplasia, and small introitus.

The chromosome 8q21.11 deletion syndrome is characterized by impaired intellectual development and common facial dysmorphic features (summary by Palomares et al., 2011).

EFEMP2-related cutis laxa, or autosomal recessive cutis laxa type 1B (ARCL1B), is characterized by cutis laxa and systemic involvement, most commonly arterial tortuosity, aneurysms, and stenosis; retrognathia; joint laxity; and arachnodactyly. Severity ranges from perinatal lethality as a result of cardiopulmonary failure to manifestations limited to the vascular and craniofacial systems.

Lethal neonatal rigidity and multifocal seizure syndrome (RMFSL) is a severe autosomal recessive epileptic encephalopathy characterized by onset of rigidity and intractable seizures at or soon after birth. Affected infants achieve no developmental milestones and die within the first months or years of life (summary by Saitsu et al., 2014).

Neurodevelopmental disorder with hypotonia, craniofacial abnormalities, and seizures (NEDHCS) is an autosomal recessive syndrome characterized primarily by hypotonia and poor feeding apparent in early infancy. Affected individuals have severe global developmental delay, early-onset intractable seizures, and recognizable craniofacial dysmorphism with skull abnormalities. The disorder is believed to be unique to the Amish population, where it exhibits a founder effect (summary by Ammous et al., 2021).

Fibrochondrogenesis is a severe skeletal dysplasia characterized by a flat midface, short long bones, short ribs with broad metaphyses, and vertebral bodies that show distinctive hypoplastic posterior ends and rounded anterior ends, giving the vertebral bodies a pinched appearance on lateral radiographic views. The chest is small, causing perinatal respiratory problems which usually, but not always, result in lethality. Affected individuals who survive the neonatal period have high myopia, mild to moderate hearing loss, and severe skeletal dysplasia (summary by Tompson et al., 2012). For a discussion of genetic heterogeneity of fibrochondrogenesis, see FBCG1 (228520).

The 17q12 recurrent duplication is characterized by intellectual abilities ranging from normal to severe disability and other variable clinical manifestations. Speech delay is common, and most affected individuals have some degree of hypotonia and gross motor delay. Behavioral and psychiatric conditions reported in some affected individuals include autism spectrum disorder, schizophrenia, and behavioral abnormalities (aggression and self-injury). Seizures are present in 75%. Additional common findings include microcephaly, ocular abnormalities, and endocrine abnormalities. Short stature and renal and cardiac abnormalities are also reported in some individuals. Penetrance is incomplete and clinical findings are variable.

The 17q12 recurrent deletion syndrome is characterized by variable combinations of the three following findings: structural or functional abnormalities of the kidney and urinary tract, maturity-onset diabetes of the young type 5 (MODY5), and neurodevelopmental or neuropsychiatric disorders (e.g., developmental delay, intellectual disability, autism spectrum disorder, schizophrenia, anxiety, and bipolar disorder). Using a method of data analysis that avoids ascertainment bias, the authors determined that multicystic kidneys and other structural and functional kidney anomalies occur in 85% to 90% of affected individuals, MODY5 in approximately 40%, and some degree of developmental delay or learning disability in approximately 50%. MODY5 is most often diagnosed before age 25 years (range: age 10-50 years).

The interstitial 16q22 deletion syndrome is a multiple congenital anomaly disorder associated with failure to thrive in infancy, poor growth, delayed psychomotor development, hypotonia, and dysmorphic features, including large anterior fontanel, high forehead, diastasis of the cranial sutures, broad nasal bridge, hypertelorism, low-set abnormal ears, and short neck. The phenotypic features and deletion sizes are variable, but deletion of 16q22 appears to be critical for manifestations of the syndrome (summary by Fujiwara et al., 1992).

Bent bone dysplasia syndrome-1 (BBDS1) is a perinatal lethal skeletal dysplasia characterized by poor mineralization of the calvarium, craniosynostosis, dysmorphic facial features, prenatal teeth, hypoplastic pubis and clavicles, osteopenia, and bent long bones (Merrill et al., 2012). Genetic Heterogeneity of Bent Bone Dysplasia Syndrome BBDS2 (620076) is caused by mutation in the LAMA5 gene (601033) on chromosome 20q13.

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure, and increased risk for malignancy. Physical abnormalities, present in approximately 75% of affected individuals, include one or more of the following: short stature, abnormal skin pigmentation, skeletal malformations of the upper and/or lower limbs, microcephaly, and ophthalmic and genitourinary tract anomalies. Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. The incidence of acute myeloid leukemia is 13% by age 50 years. Solid tumors – particularly of the head and neck, skin, and genitourinary tract – are more common in individuals with FA.

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure, and increased risk for malignancy. Physical abnormalities, present in approximately 75% of affected individuals, include one or more of the following: short stature, abnormal skin pigmentation, skeletal malformations of the upper and/or lower limbs, microcephaly, and ophthalmic and genitourinary tract anomalies. Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. The incidence of acute myeloid leukemia is 13% by age 50 years. Solid tumors – particularly of the head and neck, skin, and genitourinary tract – are more common in individuals with FA.

Craniofacial microsomia is a term used to describe a spectrum of abnormalities that primarily affect the development of the skull (cranium) and face before birth. Microsomia means abnormal smallness of body structures. Most people with craniofacial microsomia have differences in the size and shape of facial structures between the right and left sides of the face (facial asymmetry). In about two-thirds of cases, both sides of the face have abnormalities, which usually differ from one side to the other. Other individuals with craniofacial microsomia are affected on only one side of the face. The facial characteristics in craniofacial microsomia typically include underdevelopment of one side of the upper or lower jaw (maxillary or mandibular hypoplasia), which can cause dental problems and difficulties with feeding and speech. In cases of severe mandibular hypoplasia, breathing may also be affected.\n\nPeople with craniofacial microsomia usually have ear abnormalities affecting one or both ears, typically to different degrees. They may have growths of skin (skin tags) in front of the ear (preauricular tags), an underdeveloped or absent external ear (microtia or anotia), or a closed or absent ear canal; these abnormalities may lead to hearing loss. Eye problems are less common in craniofacial microsomia, but some affected individuals have an unusually small eyeball (microphthalmia) or other eye abnormalities that result in vision loss.\n\nAbnormalities in other parts of the body, such as malformed bones of the spine (vertebrae), abnormally shaped kidneys, and heart defects, may also occur in people with craniofacial microsomia.\n\nMany other terms have been used for craniofacial microsomia. These other names generally refer to forms of craniofacial microsomia with specific combinations of signs and symptoms, although sometimes they are used interchangeably. Hemifacial microsomia often refers to craniofacial microsomia with maxillary or mandibular hypoplasia. People with hemifacial microsomia and noncancerous (benign) growths in the eye called epibulbar dermoids may be said to have Goldenhar syndrome or oculoauricular dysplasia.

The peroxisome biogenesis disorder (PBD) Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 2 (CG2) have mutations in the PEX5 gene. For information on the history of PBD complementation groups, see 214100.

Cornelia de Lange syndrome (CdLS) encompasses a spectrum of findings from mild to severe. Severe (classic) CdLS is characterized by distinctive facial features, growth restriction (prenatal onset; <5th centile throughout life), hypertrichosis, and upper-limb reduction defects that range from subtle phalangeal abnormalities to oligodactyly (missing digits). Craniofacial features include synophrys, highly arched and/or thick eyebrows, long eyelashes, short nasal bridge with anteverted nares, small widely spaced teeth, and microcephaly. Individuals with a milder phenotype have less severe growth, cognitive, and limb involvement, but often have facial features consistent with CdLS. Across the CdLS spectrum IQ ranges from below 30 to 102 (mean: 53). Many individuals demonstrate autistic and self-destructive tendencies. Other frequent findings include cardiac septal defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia.

Auriculocondylar syndrome (ARCND), also known as 'question-mark ear syndrome' or 'dysgnathia complex,' is a craniofacial malformation syndrome characterized by highly variable mandibular anomalies, including mild to severe micrognathia, often with temporomandibular joint ankylosis, cleft palate, and a distinctive ear malformation that consists of separation of the lobule from the external ear, giving the appearance of a question mark. Other frequently described features include prominent cheeks, cupped and posteriorly rotated ears, preauricular tags, and microstomia (summary by Rieder et al., 2012). For a discussion of genetic heterogeneity of auriculocondylar syndrome, see ARCND1 (602483).

HCFP3 is an autosomal recessive congenital cranial dysinnervation disorder characterized by isolated dysfunction of the seventh cranial nerve resulting in facial palsy. Additional features may include orofacial anomalies, such as smooth philtrum, lagophthalmos, swallowing difficulties, and dysarthria, as well as hearing loss. There is some phenotypic overlap with Moebius syndrome (see, e.g., 157900), but patients with HCFP usually retain full eye motility or have esotropia without paralysis of the sixth cranial nerve (summary by Vogel et al., 2016). For a phenotypic description and a discussion of genetic heterogeneity of hereditary congenital facial paresis, see 601471.

Cerebellar dysfunction with variable cognitive and behavioral abnormalities (CECBA) is an autosomal dominant neurologic disorder with significant phenotypic heterogeneity, even within families. The disorder is most often diagnosed through genetic analysis with retrospective clinical phenotyping. Symptom onset is usually in early childhood, although later onset, even in adulthood, has been reported. Most affected individuals show global developmental delay from early childhood, particularly of motor and language skills. Many have mild intellectual disability; behavioral and psychiatric abnormalities such as autism and obsessive-compulsive disorder are also often observed. The movement disorder is prominent and may include cerebellar signs such as ataxia, tremor, dysmetria, poor coordination, and dysarthria. Other abnormal movements including spasticity, myoclonus, and dystonia have been reported, thus widening the phenotypic spectrum. Brain imaging is usually normal, but may show cerebellar atrophy or nonspecific white matter lesions. Variable dysmorphic facial features may also be present (summary by Thevenon et al., 2012; Jacobs et al., 2021; Wijnen et al., 2020).

Combined methylmalonic aciduria (MMA) and homocystinuria is a genetically heterogeneous metabolic disorder of cobalamin (cbl; vitamin B12) metabolism, which is essential for hematologic and neurologic function. Biochemically, the defect causes decreased levels of the coenzymes adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), which results in decreased activity of the respective enzymes methylmalonyl-CoA mutase (MUT; 609058) and methyltetrahydrofolate:homocysteine methyltransferase, also known as methionine synthase (MTR; 156570). The cblJ type is phenotypically and biochemically similar to the cblF type (MAHCF; 277380) (summary by Coelho et al., 2012).

The peroxisomal biogenesis disorder (PBD) Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 5 (CG5, equivalent to CG10 and CGF) have mutations in the PEX2 gene. For information on the history of PBD complementation groups, see 214100.

Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome resulting from disordered peroxisome biogenesis. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 12 (CG12, equivalent to CGG) have mutations in the PEX3 gene. For information on the history of PBD complementation groups, see 214100.

Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome resulting from disordered peroxisome biogenesis. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group K (CGK) have mutations in the PEX14 gene. For information on the history of PBD complementation groups, see 214100.

Pontocerebellar hypoplasia type 7 (PCH7) is a severe neurologic condition characterized by delayed psychomotor development, hypotonia, breathing abnormalities, and gonadal abnormalities (summary by Anderson et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1 (607596).

This autosomal recessive form of distal arthrogryposis, designated DA5D by McMillin et al. (2013), is characterized by severe camptodactyly of the hands, including adducted thumbs and wrists; mild camptodactyly of the toes; clubfoot and/or a calcaneovalgus deformity; extension contractures of the knee; unilateral ptosis or ptosis that is more severe on one side; a round-shaped face; arched eyebrows; a bulbous, upturned nose; and micrognathia. Notably, these patients do not have ophthalmoplegia. For a general phenotypic description and discussion of genetic heterogeneity of distal arthrogryposis, see DA1A (108120). For discussion of genetic heterogeneity of distal arthrogryposis type 5, see DA5 (108145).

Primary microcephaly-10 (MCPH10) is an autosomal recessive disorder characterized by extremely small head size (-9 SD) at birth and death usually by 1 year of age. Neuropathologic examination shows severe loss of neurons as well as neuronal loss of polarity and abnormal dendritic maturation (summary by Yang et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of primary microcephaly, see MCPH1 (251200).

PIK3CA-related overgrowth spectrum (PROS) encompasses a range of clinical findings in which the core features are congenital or early-childhood onset of segmental/focal overgrowth with or without cellular dysplasia. Prior to the identification of PIK3CA as the causative gene, PROS was separated into distinct clinical syndromes based on the tissues and/or organs involved (e.g., MCAP [megalencephaly-capillary malformation] syndrome and CLOVES [congenital lipomatous asymmetric overgrowth of the trunk, lymphatic, capillary, venous, and combined-type vascular malformations, epidermal nevi, skeletal and spinal anomalies] syndrome). The predominant areas of overgrowth include the brain, limbs (including fingers and toes), trunk (including abdomen and chest), and face, all usually in an asymmetric distribution. Generalized brain overgrowth may be accompanied by secondary overgrowth of specific brain structures resulting in ventriculomegaly, a markedly thick corpus callosum, and cerebellar tonsillar ectopia with crowding of the posterior fossa. Vascular malformations may include capillary, venous, and less frequently, arterial or mixed (capillary-lymphatic-venous or arteriovenous) malformations. Lymphatic malformations may be in various locations (internal and/or external) and can cause various clinical issues, including swelling, pain, and occasionally localized bleeding secondary to trauma. Lipomatous overgrowth may occur ipsilateral or contralateral to a vascular malformation, if present. The degree of intellectual disability appears to be mostly related to the presence and severity of seizures, cortical dysplasia (e.g., polymicrogyria), and hydrocephalus. Many children have feeding difficulties that are often multifactorial in nature. Endocrine issues affect a small number of individuals and most commonly include hypoglycemia (largely hypoinsulinemic hypoketotic hypoglycemia), hypothyroidism, and growth hormone deficiency.

\n\nThe features of Cowden syndrome overlap with those of another disorder called Bannayan-Riley-Ruvalcaba syndrome. People with Bannayan-Riley-Ruvalcaba syndrome also develop hamartomas and other noncancerous tumors.  Some people with Cowden syndrome have relatives diagnosed with Bannayan-Riley-Ruvalcaba syndrome, and other affected individuals have the characteristic features of both conditions. Based on these similarities, researchers have proposed that Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome represent a spectrum of overlapping features known as PTEN hamartoma tumor syndrome (named for the genetic cause of the conditions) instead of two distinct conditions.\n\nSome people do not meet the strict criteria for a clinical diagnosis of Cowden syndrome, but they have some of the characteristic features of the condition, particularly the cancers. These individuals are often described as having Cowden-like syndrome. Both Cowden syndrome and Cowden-like syndrome are caused by mutations in the same genes.\n\nCowden syndrome is associated with an increased risk of developing several types of cancer, particularly cancers of the breast, a gland in the lower neck called the thyroid, and the lining of the uterus (the endometrium). Other cancers that have been identified in people with Cowden syndrome include kidney cancer, colorectal cancer, and an agressive form of skin cancer called melanoma. Compared with the general population, people with Cowden syndrome develop these cancers at younger ages, often beginning in their thirties or forties. People with Cowden syndrome are also more likely to develop more than one cancer during their lifetimes compared to the general population. Other diseases of the breast, thyroid, and endometrium are also common in Cowden syndrome. Additional signs and symptoms can include an enlarged head (macrocephaly) and a rare, noncancerous brain tumor called Lhermitte-Duclos disease. A small percentage of affected individuals have delayed development, intellectual disability, or autism spectrum disorder, which can affect communication and social interaction.\n\nAlmost everyone with Cowden syndrome develops hamartomas. These growths are most commonly found on the skin and mucous membranes (such as the lining of the mouth and nose), but they can also occur in the intestine and other parts of the body. The growth of hamartomas on the skin and mucous membranes typically becomes apparent by a person's late twenties.\n\nCowden syndrome is a genetic disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers.

Short ulna-dysmorphism-hypotonia-intellectual disability syndrome is a rare, genetic, multiple congenital anomalies/dysmorphic syndrome characterized by mild to severe global development delay, severe intellectual disability, mild hypotonia, a short ulna, hirsutism of the face and extremities, minimal scoliosis, and facial dysmorphism, notably a tall broad forehead, synophrys, hypertelorism, malar hypoplasia, broad nose with thick alae nasi, low-set, small ears, long philtrum, thin upper lip and everted lower lip vermilion.

The FLNB disorders include a spectrum of phenotypes ranging from mild to severe. At the mild end are spondylocarpotarsal synostosis (SCT) syndrome and Larsen syndrome; at the severe end are the phenotypic continuum of atelosteogenesis types I (AOI) and III (AOIII) and Piepkorn osteochondrodysplasia (POCD). SCT syndrome is characterized by postnatal disproportionate short stature, scoliosis and lordosis, clubfeet, hearing loss, dental enamel hypoplasia, carpal and tarsal synostosis, and vertebral fusions. Larsen syndrome is characterized by congenital dislocations of the hip, knee, and elbow; clubfeet (equinovarus or equinovalgus foot deformities); scoliosis and cervical kyphosis, which can be associated with a cervical myelopathy; short, broad, spatulate distal phalanges; distinctive craniofacies (prominent forehead, depressed nasal bridge, malar flattening, and widely spaced eyes); vertebral anomalies; and supernumerary carpal and tarsal bone ossification centers. Individuals with SCT syndrome and Larsen syndrome can have midline cleft palate and hearing loss. AOI and AOIII are characterized by severe short-limbed dwarfism; dislocated hips, knees, and elbows; and clubfeet. AOI is lethal in the perinatal period. In individuals with AOIII, survival beyond the neonatal period is possible with intensive and invasive respiratory support. Piepkorn osteochondrodysplasia (POCD) is a perinatal-lethal micromelic dwarfism characterized by flipper-like limbs (polysyndactyly with complete syndactyly of all fingers and toes, hypoplastic or absent first digits, and duplicated intermediate and distal phalanges), macrobrachycephaly, prominant forehead, hypertelorism, and exophthalmos. Occasional features include cleft palate, omphalocele, and cardiac and genitourinary anomalies. The radiographic features at mid-gestation are characteristic.

MED12-related disorders include the phenotypes of FG syndrome type 1 (FGS1), Lujan syndrome (LS), X-linked Ohdo syndrome (XLOS), Hardikar syndrome (HS), and nonspecific intellectual disability (NSID). FGS1 and LS share the clinical findings of cognitive impairment, hypotonia, and abnormalities of the corpus callosum. FGS1 is further characterized by absolute or relative macrocephaly, tall forehead, downslanted palpebral fissures, small and simple ears, constipation and/or anal anomalies, broad thumbs and halluces, and characteristic behavior. LS is further characterized by large head, tall thin body habitus, long thin face, prominent nasal bridge, high narrow palate, and short philtrum. Carrier females in families with FGS1 and LS are typically unaffected. XLOS is characterized by intellectual disability, blepharophimosis, and facial coarsening. HS has been described in females with cleft lip and/or cleft palate, biliary and liver anomalies, intestinal malrotation, pigmentary retinopathy, and coarctation of the aorta. Developmental and cognitive concerns have not been reported in females with HS. Pathogenic variants in MED12 have been reported in an increasing number of males and females with NSID, with affected individuals often having clinical features identified in other MED12-related disorders.

Meckel syndrome, also known as Meckel-Gruber syndrome, is a severe pleiotropic autosomal recessive developmental disorder caused by dysfunction of primary cilia during early embryogenesis. There is extensive clinical variability and controversy as to the minimum diagnostic criteria. Early reports, including that of Opitz and Howe (1969) and Wright et al. (1994), stated that the classic triad of Meckel syndrome comprises (1) cystic renal disease; (2) a central nervous system malformation, most commonly occipital encephalocele; and (3) polydactyly, most often postaxial. However, based on a study of 67 patients, Salonen (1984) concluded that the minimum diagnostic criteria are (1) cystic renal disease; (2) CNS malformation, and (3) hepatic abnormalities, including portal fibrosis or ductal proliferation. In a review of Meckel syndrome, Logan et al. (2011) stated that the classic triad first described by Meckel (1822) included occipital encephalocele, cystic kidneys, and fibrotic changes to the liver. Genetic Heterogeneity of Meckel Syndrome See also MKS2 (603194), caused by mutation in the TMEM216 gene (613277) on chromosome 11q12; MKS3 (607361), caused by mutation in the TMEM67 gene (609884) on chromosome 8q; MKS4 (611134), caused by mutation in the CEP290 gene (610142) on chromosome 12q; MKS5 (611561), caused by mutation in the RPGRIP1L gene (610937) on chromosome 16q12; MKS6 (612284), caused by mutation in the CC2D2A gene (612013) on chromosome 4p15; MKS7 (267010), caused by mutation in the NPHP3 (608002) gene on chromosome 3q22; MKS8 (613885), caused by mutation in the TCTN2 gene (613846) on chromosome 12q24; MKS9 (614209), caused by mutation in the B9D1 gene (614144) on chromosome 17p11; MKS10 (614175), caused by mutation in the B9D2 gene (611951) on chromosome 19q13; MKS11 (615397), caused by mutation in the TMEM231 gene (614949) on chromosome 16q23; MKS12 (616258), caused by mutation in the KIF14 gene (611279) on chromosome 1q32; MKS13 (617562), caused by mutation in the TMEM107 gene (616183) on chromosome 17p13; and MKS14 (619879), caused by mutation in the TXNDC15 gene (617778) on chromosome 5q31.

Mandibular hypoplasia, deafness, progeroid features, and lipodystrophy syndrome (MDPL) is an autosomal dominant systemic disorder characterized by prominent loss of subcutaneous fat, a characteristic facial appearance, and metabolic abnormalities including insulin resistance and diabetes mellitus. Sensorineural deafness occurs late in the first or second decades of life (summary by Weedon et al., 2013).

The features of Ehlers-Danlos syndrome spondylodysplastic type 2 (EDSSPD2) include an aged appearance, developmental delay, short stature, craniofacial disproportion, generalized osteopenia, defective wound healing, hypermobile joints, hypotonic muscles, and loose but elastic skin (Okajima et al., 1999). For a discussion of genetic heterogeneity of the spondylodysplastic type of Ehlers-Danlos syndrome, see 130070.

Infantile hypotonia with psychomotor retardation and characteristic facies (IHPRF) is a severe autosomal recessive neurologic disorder with onset at birth or in early infancy. Affected individuals show very poor, if any, normal cognitive development. Some patients are never learn to sit or walk independently (summary by Al-Sayed et al., 2013). Genetic Heterogeneity of Infantile Hypotonia with Psychomotor Retardation and Characteristic Facies See also IHPRF2 (616801), caused by mutation in the UNC80 gene (612636) on chromosome 2q34; and IHPRF3 (616900), caused by mutation in the TBCK gene (616899) on chromosome 4q24.

A rare, genetic, neurodevelopmental disorder characterized by global developmental delay, borderline to severe intellectual disability, feeding difficulties, behavioral anomalies, vision anomalies and mild facial dysmorphism. Other associated features may include microcephaly, short stature, urogenital or palatal anomalies (e.g. cleft palate), minor cardiac defects, recurrent infections or hearing loss.

Syndromic microphthalmia-12 is a rare disease characterized by bilateral small eyeballs (microphthalmia), lungs that are too small (pulmonary hypoplasia), and a defect or hole in the diaphragm that allows the abdominal contents to move into the chest cavity (diaphragmatic hernia). Other symptoms may include: Severe global developmental delay with progressive motor impairment due to spasticity and/or uncontrolled repetitive muscular contractions (dystonia), with or without abnormal quick movements that resemble dancing (chorea), Defects of the cerebellum (Chiari type I malformation) Accumulation of cerebrospinal fluid inside the brain (hydrocephaly), Severe feeding difficulties, Mild facial dysmorphism with broad nasal root and tip, and a very small chin (micrognathia), Severe language delay, Wheelchair-bound. Syndromic microphthalmia-12 is caused by mutations in the RARB gene. There is no specific treatment for this syndrome.

Van Maldergem syndrome is an autosomal recessive disorder characterized by intellectual disability, typical craniofacial features, auditory malformations resulting in hearing loss, and skeletal and limb malformations. Some patients have renal hypoplasia. Brain MRI typically shows periventricular nodular heterotopia (summary by Cappello et al., 2013). For a discussion of genetic heterogeneity of Van Maldergem syndrome, see 601390.

Asparagine synthetase deficiency (ASD) mainly presents as a triad of congenital microcephaly, severe developmental delay, and axial hypotonia followed by spastic quadriplegia. Low cerebrospinal fluid (CSF) asparagine level can help the clinician in differentiating this disorder from others. In most cases age of onset of apnea, excessive irritability, and seizures is soon after birth. Affected individuals typically do not acquire any developmental milestones. Spastic quadriplegia can lead to severe contractures of the limbs and neurogenic scoliosis. Feeding difficulties (gastroesophageal reflux disease, frequent vomiting, swallowing dysfunction, and gastroesophageal incoordination) are a significant problem in most affected individuals. A majority have cortical blindness. MRI findings are nonspecific but may include generalized atrophy and simplified gyral pattern.

PDE4D haploinsufficiency syndrome is a rare syndromic intellectual disability characterized by developmental delay, intellectual disability, low body mass index, long arms, fingers and toes, prominent nose and small chin.

Auriculocondylar syndrome (ARCND) is a rare craniofacial disorder involving first and second pharyngeal arch derivatives and includes the key features of micrognathia, temporomandibular joint and condyle anomalies, microstomia, prominent cheeks, and question mark ears (QMEs). QMEs consist of a defect between the lobe and the upper two-thirds of the pinna, ranging from a mild indentation in the helix to a complete cleft between the lobe and helix (summary by Gordon et al., 2013). For a general phenotypic description and discussion of genetic heterogeneity of auriculocondylar syndrome, see ARCND1 (602483).

Nemaline myopathy-9 is an autosomal recessive muscle disorder characterized by onset of muscle weakness in early infancy. The phenotype is highly variable, ranging from death in infancy due to lack of antigravity movements, to slowly progressive distal muscle weakness with preserved ambulation later in childhood. Muscle biopsy shows typical rod-like structure in myofibers (summary by Gupta et al., 2013). For a discussion of genetic heterogeneity of nemaline myopathy, see 161800.

Intellectual disability-facial dysmorphism syndrome due to SETD5 haploinsufficiency is a rare, syndromic intellectual disability characterized by intellectual disability of various severity, hypotonia, feeding difficulties, dysmorphic features, autism and behavioral issues. Growth retardation, congenital heart anomalies, gastrointestinal and genitourinary defects have been rarely associated.

Seckel syndrome-8 (SCKL8) is characterized by severe microcephaly and markedly reduced height. Some patients have bird-like facies and exhibit developmental delays (Shaheen et al., 2014; Tarnauskaite et al., 2019). For a discussion of genetic heterogeneity of Seckel syndrome, see SCKL1 (210600).

Tetraamelia syndrome-1 (TETAMS1) is characterized by complete limb agenesis without defects of scapulae or clavicles. Other features include bilateral cleft lip/palate, diaphragmatic defect with bilobar right lung, renal and adrenal agenesis, pelvic hypoplasia, and urogenital defects (Niemann et al., 2004). Genetic Heterogeneity of tetraamelia syndrome Tetraamelia syndrome-2 (TETAMS2; 618021) is caused by mutation in the RSPO2 gene (610575) on chromosome 8q23.

Congenital disorder of glycosylation type Iy (CDG1Y) is an X-linked disorder characterized by developmental delay, speech delay, impaired intellectual development, muscular hypotonia, microcephaly, and distinctive facial features (summary by Johnsen et al., 2024).

The main features of Xia-Gibbs syndrome (XGS), present in a majority of affected individuals, include delayed motor milestones, speech delay with severely limited or absent speech, moderate-to-severe cognitive impairment, hypotonia, structural brain anomalies, and nonspecific dysmorphic features. Other features may include sleep apnea, movement disorders (ataxia, tremors, and bradykinesias) that often become apparent in childhood or adolescence, short stature, seizures, eye anomalies, behavioral concerns, autism spectrum disorder, scoliosis, and laryngomalacia.

A rare genetic syndromic intellectual disability characterized by global developmental delay and borderline to severe intellectual disability, autism spectrum disorder with obsessive behavior, stereotypies, hyperactivity but frequently friendly and affable personality, feeding difficulties, short stature, muscular hypotonia, microcephaly, characteristic dysmorphic features (hypertelorism, high arched eyebrows, ptosis, deep and/or broad nasal bridge, broad/prominent nasal tip, short and/or upturned philtrum, narrow mouth, and micrognathia), and skeletal anomalies (kyphosis and/or scoliosis, arthrogryposis, slender habitus and extremities). Other clinical features may include hernias, congenital heart defects, cryptorchidism and seizures.

Pontocerebellar hypoplasia type 2E is an autosomal recessive neurodegenerative disorder characterized by profound mental retardation, progressive microcephaly, spasticity, and early-onset epilepsy (summary by Feinstein et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of pontocerebellar hypoplasia type 2, see PCH2A (277470).

Centronuclear myopathy-5 (CNM5) is an autosomal recessive congenital myopathy characterized by severe neonatal hypotonia with respiratory insufficiency and difficulty feeding. Some patients die in infancy, and some develop dilated cardiomyopathy. Children show severely delayed motor development (summary by Agrawal et al., 2014). For a discussion of genetic heterogeneity of centronuclear myopathy, see CNM1 (160150).

CAGSSS, which comprises cataracts, growth hormone deficiency, sensory neuropathy, sensorineural hearing loss, and skeletal dysplasia, is an autosomal recessive multisystemic disorder with a highly variable phenotypic spectrum. Not all of these features are always present, and almost all the features may present at different times and/or become more apparent with age. The skeletal features are consistent with spondyloepimetaphyseal dysplasia (SEMD) (summary by Vona et al., 2018). One family had a distinctive presentation with infantile-onset intractable seizures and cortical abnormalities reminiscent of Leigh syndrome (see 256000). The correlation between genotype and phenotype remains unclear, but since the IARS2 gene is involved in mitochondrial function, heterogeneous manifestations can be expected (Takezawa et al., 2018).

Neu-Laxova syndrome-2 (NLS2) is a rare autosomal recessive disorder characterized by a recognizable pattern of severe congenital malformations leading to prenatal or early postnatal lethality. Affected individuals have abnormal craniofacial features, microcephaly, intrauterine growth retardation, ichthyosis, flexion deformities, limb malformations, and edema of the hands and feet. Some patients have malformations of the central nervous system, such as abnormal gyration (summary by Acuna-Hidalgo et al., 2014). For a discussion of genetic heterogeneity of Neu-Laxova syndrome, see NLS1 (256520).

Any autosomal recessive primary microcephaly in which the cause of the disease is a mutation in the CENPE gene.

Microcephaly and chorioretinopathy-2 is an autosomal recessive developmental disorder characterized by delayed psychomotor development, visual impairment, and short stature (summary by Martin et al., 2014). For a discussion of genetic heterogeneity of microcephaly and chorioretinopathy, see MCCRP1 (251270).

Ruijs et al. (2003) reported a Moroccan boy with a chromosomal breakage who died of hepatocellular carcinoma at age 17 years. The boy was noted to have growth retardation at age 3 years; at age 7 he was found to have thoracic kyphosis, frontal bossing, and a delayed bone age of approximately 3 years. He underwent surgery for severe bilateral posterior subcapsular cataracts at age 14. Examination at age 15 showed short stature and low weight, with premature graying of scalp hair, small frontotemporal diameter, small deep-set eyes, bulbous nose with high nasal bridge, small upper lip, and micrognathia. In addition, he had thoracic kyphoscoliosis, sloping shoulders, mild pectus excavatum, moderate bilateral contractures of both elbows, bilateral clinodactyly, and pes planus. At age 17, he developed abdominal pain, and ultrasonography revealed a liver mass; biopsy confirmed hepatocellular carcinoma. Because of the advanced stage, no treatment was possible, and he died 2 months later. Although his parents were not known to be consanguineous, they originated from the same small Moroccan village. Lessel et al. (2014) studied 2 brothers from a nonconsanguineous Australian family of European ancestry who exhibited low body weight, micrognathia, triangular face, muscular atrophy, lipodystrophy, bilateral simian creases, delayed bone age, and mild joint restrictions in the fingers and elbows. In addition, both brothers developed early-onset hepatocellular carcinoma, at ages 16 and 14 years, respectively. The older brother died at age 18 from complications of acute fulminant hepatic failure. Analysis of patient tumor biopsies showed strong focal accumulations of cancer biomarkers as well as a high proliferative index compared to healthy liver or to cells from idiopathic hepatocellular carcinoma.

Developmental and epileptic encephalopathy-28 (DEE28) is an autosomal recessive severe neurologic disorder characterized by the onset of refractory seizures in the first months of life. Affected individuals have severe axial hypotonia and profoundly impaired psychomotor development. More severely affected patients have acquired microcephaly, poor or absent visual contact, and retinal degeneration; early death may occur (summary by Mignot et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Temple syndrome is a short stature disorder of imprinting. The cardinal features are low birth weight, hypotonia and motor delay, feeding problems early in life, early puberty, and significantly reduced final height. Facial features include a broad forehead and short nose with a wide nasal tip, and the majority of patients have small hands and feet. However, many of the clinical features are nonspecific, making diagnosis difficult. In addition, isodisomy may uncover recessive disorders, which may influence the phenotype in maternal uniparental disomy of chromosome 14 (UPD14mat) cases (summary by Ioannides et al., 2014).

A rare genetic developmental defect during embryogenesis malformation syndrome with characteristics of intrauterine growth restriction, flexion arthrogryposis of all joints, severe microcephaly, renal cystic dysplasia/agenesis/hypoplasia and complex malformations of the brain (cerebral and cerebellar hypoplasia, vermis, corpus callosum and/or occipital lobe agenesis, with or without arhinencephaly), as well as of the genitourinary tract (ureteral agenesis/hypoplasia, uterine hypoplasia and/or vaginal atresia), leading to fetal demise.

Any spondyloepimetaphyseal dysplasia with joint laxity in which the cause of the disease is a mutation in the B3GALT6 gene.

Male EBP disorder with neurologic defects (MEND) is an X-linked recessive disorder representing a continuous phenotypic spectrum with variable manifestations associated with a defect in sterol biosynthesis. Features include intellectual disability, short stature, scoliosis, digital abnormalities, cataracts, and dermatologic abnormalities. Not all patients show all features, and the severity is highly variable. Molecular studies indicate that affected males are hemizygous for a nonmosaic hypomorphic EBP allele. Carrier females are generally clinically asymptomatic, but may show biochemical abnormalities (summary by Arnold et al., 2012 and Barboza-Cerda et al., 2014).

Complex lethal osteochondrodysplasia of the Symoens-Barnes-Gistelinck type is characterized by severe skeletal osteopenia, microcephaly, multiple fractures, and congenital anomalies including ascites, pleural effusion, and intracranial ventriculomegaly (Symoens et al., 2015).

Autosomal dominant Robinow syndrome (ADRS) is characterized by skeletal findings (short stature, mesomelic limb shortening predominantly of the upper limbs, and brachydactyly), genital abnormalities (in males: micropenis / webbed penis, hypoplastic scrotum, cryptorchidism; in females: hypoplastic clitoris and labia majora), dysmorphic facial features (widely spaced and prominent eyes, frontal bossing, anteverted nares, midface retrusion), dental abnormalities (including malocclusion, crowding, hypodontia, late eruption of permanent teeth), bilobed tongue, and occasional prenatal macrocephaly that persists postnatally. Less common findings include renal anomalies, radial head dislocation, vertebral abnormalities such as hemivertebrae and scoliosis, nail dysplasia, cardiac defects, cleft lip/palate, and (rarely) cognitive delay. When present, cardiac defects are a major cause of morbidity and mortality. A variant of Robinow syndrome, associated with osteosclerosis and caused by a heterozygous pathogenic variant in DVL1, is characterized by normal stature, persistent macrocephaly, increased bone mineral density with skull osteosclerosis, and hearing loss, in addition to the typical features described above.

Lymphatic malformation-6 is a form of generalized lymphatic dysplasia (GLD), which is characterized by a uniform, widespread lymphedema affecting all segments of the body, with systemic involvement such as intestinal and/or pulmonary lymphangiectasia, pleural effusions, chylothoraces and/or pericardial effusions. In LMPHM6, there is a high incidence of nonimmune hydrops fetalis (NIHF) with either death or complete resolution of the neonatal edema, but childhood onset of lymphedema with or without systemic involvement also occurs. Mild facial edema is often present. Patients have normal intelligence and no seizures (summary by Fotiou et al., 2015). For a discussion of genetic heterogeneity of lymphatic malformation, see 153100.

Microcephaly, short stature, and impaired glucose metabolism-2 (MSSGM2) is an autosomal recessive syndrome characterized by microcephaly associated with impaired intellectual development, and short stature. Patients develop diabetes in the second or third decade of life, and hypothyroidism and delayed puberty have also been reported (Abdulkarim et al., 2015; Kernohan et al., 2015). For a discussion of genetic heterogeneity of microcephaly, short stature, and impaired glucose metabolism, see MSSGM1 (616033).

Any Seckel syndrome in which the cause of the disease is a mutation in the TRAIP gene.

Congenital symmetric circumferential skin creases is characterized by the folding of excess skin, which leads to ringed creases, primarily of the limbs. Affected individuals also exhibit intellectual disability, cleft palate, and dysmorphic features (summary by Isrie et al., 2015). For a discussion of genetic heterogeneity of congenital symmetric circumferential skin creases, see CSCSC1 (156610).

Nephrotic syndrome type 11 (NPHS11) is an autosomal recessive disorder of the kidney with onset in the first decade of life. The disorder is progressive and usually results in end-stage renal disease necessitating renal transplantation, although some patients may have a slightly milder phenotype (Miyake et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of nephrotic syndrome, see NPHS1 (256300).

Congenital myasthenic syndrome-19 (CMS19) is an autosomal recessive disorder resulting from a defect in the neuromuscular junction, causing generalized muscle weakness, exercise intolerance, and respiratory insufficiency. Patients present with hypotonia, feeding difficulties, and respiratory problems soon after birth, but the severity of the weakness and disease course is variable (summary by Logan et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462).

Klippel-Feil syndrome-4 with nemaline myopathy and facial dysmorphism (KFS4) is an autosomal recessive disorder characterized mainly by severe hypotonia apparent from infancy. Klippel-Feil anomaly is primarily defined by fusion of the cervical spine, with associated low posterior hairline and limited neck mobility being observed in about half of patients (summary by Alazami et al., 2015). For a general description and a discussion of genetic heterogeneity of Klippel-Feil syndrome, see KFS1 (118100).

PI4KA-related disorder is a clinically variable disorder characterized primarily by neurologic dysfunction (limb spasticity, developmental delay, intellectual disability, seizures, ataxia, nystagmus), gastrointestinal manifestations (multiple intestinal atresia, inflammatory bowel disease), and combined immunodeficiency (leukopenia, variable immunoglobulin defects). Age of onset is typically antenatal or in early childhood; individuals can present with any combination of these features. Rare individuals present with later-onset hereditary spastic paraplegia. Brain MRI findings can include hypomyelinating leukodystrophy, cerebellar hypoplasia/atrophy, thin or dysplastic corpus callosum, and/or perisylvian polymicrogyria.

Lethal congenital contracture syndrome-9 (LCCS9) is an autosomal recessive disorder characterized by multiple flexion and extension contractures resulting from reduced or absent fetal movement (Ravenscroft et al., 2015). For a general phenotypic description and discussion of genetic heterogeneity of lethal congenital contracture syndrome, see LCCS1 (253310).

The Cincinnati type of acrofacial dysostosis is a ribosomopathy characterized by a spectrum of mandibulofacial dysostosis phenotypes, with or without extrafacial skeletal defects (Weaver et al., 2015). In addition, a significant number of neurologic abnormalities have been reported, ranging from mild delays to refractory epilepsy, as well as an increased incidence of congenital heart defects, primarily septal in nature (Smallwood et al., 2023).

A rare mandibulofacial dysostosis with the association with scalp alopecia and sparse eyebrows and eyelashes. Craniofacial dysmorphic features include zygomatic and mandibular dysplasia or hypoplasia, cleft palate, micrognathia, dental anomalies, auricular dysmorphism and eyelid anomalies among others. Patients may experience limited jaw mobility, glossoptosis, upper airway obstruction and conductive hearing loss.

White-Sutton syndrome is a neurodevelopmental disorder characterized by a wide spectrum of cognitive dysfunction, developmental delays (particularly in speech and language acquisition), hypotonia, autism spectrum disorder, and other behavioral problems. Additional features commonly reported include seizures, refractive errors and strabismus, hearing loss, sleep disturbance (particularly sleep apnea), feeding and gastrointestinal problems, mild genital abnormalities in males, and urinary tract involvement in both males and females.

Lissencephaly-7 with cerebellar hypoplasia (LIS7) is a severe neurodevelopmental disorder characterized by lack of psychomotor development, facial dysmorphism, arthrogryposis, and early-onset intractable seizures resulting in death in infancy (Magen et al., 2015). For a general description and a discussion of genetic heterogeneity of lissencephaly, see LIS1 (607432).

Autosomal dominant Robinow syndrome (ADRS) is characterized by skeletal findings (short stature, mesomelic limb shortening predominantly of the upper limbs, and brachydactyly), genital abnormalities (in males: micropenis / webbed penis, hypoplastic scrotum, cryptorchidism; in females: hypoplastic clitoris and labia majora), dysmorphic facial features (widely spaced and prominent eyes, frontal bossing, anteverted nares, midface retrusion), dental abnormalities (including malocclusion, crowding, hypodontia, late eruption of permanent teeth), bilobed tongue, and occasional prenatal macrocephaly that persists postnatally. Less common findings include renal anomalies, radial head dislocation, vertebral abnormalities such as hemivertebrae and scoliosis, nail dysplasia, cardiac defects, cleft lip/palate, and (rarely) cognitive delay. When present, cardiac defects are a major cause of morbidity and mortality. A variant of Robinow syndrome, associated with osteosclerosis and caused by a heterozygous pathogenic variant in DVL1, is characterized by normal stature, persistent macrocephaly, increased bone mineral density with skull osteosclerosis, and hearing loss, in addition to the typical features described above.

Lethal congenital contracture syndrome-7, an axoglial form of arthrogryposis multiplex congenita (AMC), is characterized by congenital distal joint contractures, polyhydramnios, reduced fetal movements, and severe motor paralysis leading to death early in the neonatal period (Laquerriere et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of lethal congenital contracture syndrome, see LCCS1 (253310).

CLIFAHDD is a congenital disorder characterized by congenital contractures of the limbs and face, resulting in characteristic facial features, hypotonia, and variable degrees of developmental delay. All reported cases have occurred de novo (summary by Chong et al., 2015).

Fast-channel congenital myasthenic syndrome (FCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the acetylcholine receptor (AChR) channel, specifically from abnormally brief opening and activity of the channel, with a rapid decay in endplate current and a failure to reach the threshold for depolarization. Treatment with pyridostigmine or amifampridine may be helpful; quinine, quinidine, and fluoxetine should be avoided (summary by Sine et al., 2003 and Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462).

Any Diamond-Blackfan anemia in which the cause of the disease is a mutation in the RPS28 gene.

Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia or no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

Tonne-Kalscheuer syndrome (TOKAS) is an X-linked recessive multiple congenital anomaly disorder with 2 main presentations. Most patients exhibit global developmental delay apparent from early infancy, impaired intellectual development, speech delay, behavioral abnormalities, and abnormal gait. Affected individuals also have dysmorphic facial features that evolve with age, anomalies of the hands, feet, and nails, and urogenital abnormalities with hypogenitalism. A subset of more severely affected males develop congenital diaphragmatic hernia in utero, which may result in perinatal or premature death. Carrier females may have very mild skeletal or hormonal abnormalities (summary by Frints et al., 2019). Also see Fryns syndrome (229850), an autosomal recessive disorder with overlapping features.

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is a genetically heterogeneous autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and early death. The phenotype commonly includes cobblestone (type II) lissencephaly, cerebellar malformations, and retinal malformations. More variable features include macrocephaly or microcephaly, hypoplasia of midline brain structures, ventricular dilatation, microphthalmia, cleft lip/palate, and congenital contractures (Dobyns et al., 1989). Those with a more severe phenotype characterized as Walker-Warburg syndrome often die within the first year of life, whereas those characterized as having muscle-eye-brain disease may rarely acquire the ability to walk and to speak a few words. These are part of a group of disorders resulting from defective glycosylation of DAG1 (128239), collectively known as 'dystroglycanopathies' (Godfrey et al., 2007). Genetic Heterogeneity of Congenital Muscular Dystrophy-Dystroglycanopathy with Brain and Eye Anomalies (Type A) Muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A) is genetically heterogeneous and can be caused by mutation in other genes involved in DAG1 glycosylation: see MDDGA2 (613150), caused by mutation in the POMT2 gene (607439); MDDGA3 (253280), caused by mutation in the POMGNT1 gene (606822); MDDGA4 (253800), caused by mutation in the FKTN gene (607440); MDDGA5 (613153), caused by mutation in the FKRP gene (606596); MDDGA6 (613154), caused by mutation in the LARGE gene (603590); MDDGA7 (614643), caused by mutation in the ISPD gene (CRPPA; 614631); MDDGA8 (614830) caused by mutation in the GTDC2 gene (POMGNT2; 614828); MDDGA9 (616538), caused by mutation in the DAG1 gene (128239); MDDGA10 (615041), caused by mutation in the TMEM5 gene (RXYLT1; 605862); MDDGA11 (615181), caused by mutation in the B3GALNT2 gene (610194); MDDGA12 (615249), caused by mutation in the SGK196 gene (POMK; 615247); MDDGA13 (615287), caused by mutation in the B3GNT1 gene (B4GAT1; 605517); and MDDGA14 (615350), caused by mutation in the GMPPB gene (615320).

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome type 2, a form of MRKH syndrome (see this term), is characterized by congenital aplasia of the uterus and upper 2/3 of the vagina that is associated with at least one other malformation such as renal, vertebral, or, less commonly, auditory and cardiac defects. The acronym MURCS (MÜllerian duct aplasia, Renal dysplasia, Cervical Somite anomalies) is also used.

A rare syndromic optic nerve hypoplasia with characteristics of coloboma, osteopetrosis (particularly of the anterior ribs and femoral heads), severe microphthalmia, macrocephaly, albinism, and profound congenital deafness. Patients may also have additional eye anomalies including microcornea with pannus, dense bilateral cataracts, and translucent irides. Craniofacial dysmorphism (including frontal bossing, shallow orbits, preauricular pits, posteriorly rotated ears, micrognathia and wide palatine ridges) is also reported.

Myofibrillar myopathy-8 (MFM8) is an autosomal recessive myopathy characterized by slowly progressive proximal muscle weakness and atrophy affecting the upper and lower limbs, resulting in increased falls, gait problems, difficulty running or climbing stairs, and upper limb weakness or scapular winging. Some patients develop distal muscle weakness and atrophy. The phenotype may also be consistent with a clinical diagnosis of limb-girdle muscular dystrophy (LGMD). Age at symptom onset ranges from infancy to adulthood. Ambulation is generally preserved and cardiac involvement is rare, but respiratory compromise with decreased forced vital capacity often occurs. Muscle biopsy shows a mix of myopathic features, including myofibrillar inclusions and sarcomeric disorganization; some patients have been reported to have dystrophic changes on muscle biopsy (O'Grady et al., 2016; Daimaguler et al., 2021). There is significant phenotypic variation, even in patients with the same mutation, which must be taken into account when counseling affecting individuals (Woods et al., 2020). For a general phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy, see MFM1 (601419).

Any primary immunodeficiency disease in which the cause of the disease is a mutation in the BCL11B gene.

Combined oxidative phosphorylation deficiency-31 is an autosomal recessive multisystem disorder characterized by left ventricular noncompaction (LVNC), global developmental delay, and severe hypotonia. More variable features include seizures, cataract, and abnormal movements. The disorder becomes apparent soon after birth or in early infancy, and patients may die in early childhood. Biochemical studies are consistent with a defect in mitochondrial function (summary by Eldomery et al., 2016). For a discussion of genetic heterogeneity of combined oxidative phosphorylation deficiency, see COXPD1 (609060).

Periventricular nodular heterotopia-7 (PVNH7) is a neurologic disorder characterized by abnormal neuronal migration during brain development resulting in delayed psychomotor development and intellectual disability; some patients develop seizures. Other features include cleft palate and 2-3 toe syndactyly (summary by Broix et al., 2016). For a phenotypic description and a discussion of genetic heterogeneity of periventricular heterotopia, see 300049.

Harel-Yoon syndrome is a syndromic neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, truncal hypotonia, spasticity, and peripheral neuropathy. Other more variable features such as optic atrophy may also occur. Laboratory studies in some patients show evidence of mitochondrial dysfunction (summary by Harel et al., 2016).

The core features of short stature-micrognathia syndrome (SSMG) are intrauterine growth restriction (IUGR), postnatal short stature that is often rhizomelic, and micrognathia. Other common features include preterm birth, microcephaly, developmental delay, and genitourinary malformations in males. Transient liver dysfunction and glycosylation abnormalities during illness, giant cell hepatitis, hepatoblastoma, and cataracts have also been observed. Inter- and intrafamilial phenotypic severity varies greatly, from a relatively mild disorder to intrauterine death or stillbirth (Ritter et al., 2022).

Individuals with Okur-Chung neurodevelopmental syndrome (OCNDS) frequently have nonspecific clinical features, delayed language development, motor delay, intellectual disability (typically in the mild-to-moderate range), generalized hypotonia starting in infancy, difficulty feeding, and nonspecific dysmorphic facial features. Developmental delay affects all areas of development, but language is more impaired than gross motor skills in most individuals. Intellectual disability has been reported in about three quarters of individuals. Less common findings may include kyphoscoliosis, postnatal short stature, disrupted circadian rhythm leading to sleep disturbance, seizures, and poor coordination.

TRIO-related intellectual disability (ID) is characterized by delay in acquisition of motor and language skills, mild to borderline intellectual disability, and neurobehavioral problems (including autistic traits or autism spectrum disorder, attention-deficit/hyperactivity disorder, and/or aggression). Neonatal or infantile feeding difficulties including poor suck, impaired bottle feeding, and failure to thrive are common and are often the presenting finding. Other findings can include microcephaly, variable hand and dental abnormalities, and suggestive facial features. Only ten of the 20 individuals with a TRIO pathogenic variant reported to date had sufficient information to make preliminary generalizations about clinical manifestations; it is anticipated that the phenotype of this newly described disorder will continue to evolve.

Bone marrow failure syndrome-3 is an autosomal recessive disorder characterized by onset of pancytopenia in early childhood. Patients may have additional variable nonspecific somatic abnormalities, including poor growth, microcephaly, and skin anomalies (summary by Tummala et al., 2016). BMFS3 has a distinct phenotype and may include features that overlap with Shwachman-Diamond syndrome (SDS1; 260400), such as pancreatic insufficiency and short stature, and with dyskeratosis congenita (see, e.g., DKCA1, 127550), such as dental and hair abnormalities and shortened telomeres. In addition, some patients may have joint and skeletal abnormalities, impaired development, and retinal dysplasia (summary by D'Amours et al., 2018). For a discussion of genetic heterogeneity of BMFS, see BMFS1 (614675).

RERE-related disorders are characterized by neurodevelopmental problems with or without structural anomalies of the eyes, heart, kidneys, and genitourinary tract and mild sensorineural hearing loss. Hypotonia and feeding problems are common among affected individuals. Developmental delay and intellectual disability range from mild to profound. Behavior problems may include attention-deficit/hyperactivity disorder, self-injurious behavior, and autism spectrum disorder. A variety of eye anomalies (coloboma, optic nerve anomalies, microphthalmia, and/or Peter's anomaly) and vision issues (myopia, anisometropia, astigmatism, exotropia, esotropia) have been reported. Congenital heart defects, most commonly septal defects, have also been described. Genitourinary abnormalities include vesicoureteral reflux, and cryptorchidism and hypospadias in males. Sensorineural hearing loss can be unilateral or bilateral.

A rare genetic multiple congenital anomalies/dysmorphic syndrome with characteristics of craniofacial dysmorphism (including an abnormal skull shape, hypertelorism, downslanting palpebral fissures, epicanthal folds, low-set ears, depressed nasal bridge, micrognathia), short stature, ectodermal anomalies (such as sparse eyebrows, eyelashes, and scalp hair, hypoplastic toenails), developmental delay, and intellectual disability. Additional features may include cerebral/cerebellar malformations and mild renal involvement.

Midface hypoplasia, hearing impairment, elliptocytosis, and nephrocalcinosis is an X-linked recessive disorder with onset of features in early childhood. Anemia is sometimes present. Some patients may show mild early motor or speech delay, but cognition is normal (summary by Andreoletti et al., 2017).

Most individuals with HNRNPH2-related neurodevelopmental disorder (HNRNPH2-NDD) have symptoms early in life, before age 12 months. The major features of HNRNPH2-NDD are developmental delay / intellectual disability, motor and language delays, behavioral and psychiatric disorders, and growth and musculoskeletal abnormalities. Minor features include dysmorphic facies, gastrointestinal disturbances, epilepsy, and visual defects. Although HNRNPH2-NDD is an X-linked condition, there is not enough information on affected females versus affected males to make any generalizations about phenotypic differences between the two sexes.

BCL11A-related intellectual disability (BCL11A-ID) is characterized by developmental delay / intellectual disability of variable degree, neonatal hypotonia, microcephaly, distinctive but variable facial characteristics, behavior problems, and asymptomatic persistence of fetal hemoglobin. Growth delay, seizures, and autism spectrum disorder have also been reported in some affected individuals.

Distal chromosome 19q13.11 deletion syndrome is an autosomal dominant neurodevelopmental disorder characterized by poor overall growth, slender habitus, microcephaly, delayed development, intellectual disability with poor or absent speech, and feeding difficulties. Additional features include dysmorphic facies, signs of ectodermal dysplasia, hand and foot anomalies, and genitourinary anomalies, particularly in males (summary by Chowdhury et al., 2014).

Cole-Carpenter syndrome is characterized by bone fragility, craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features (Cole and Carpenter, 1987). Genetic Heterogeneity of Cole-Carpenter Syndrome Cole-Carpenter syndrome-2 (CLCRP2; 616294) is caused by mutation in the SEC24D gene (607186).

AMC1 is an autosomal recessive severe neurologic disorder with onset in utero. Most affected individuals die in utero or are subject to pregnancy termination because of lack of fetal movements and prenatal evidence of contractures of virtually all joints. Those who survive have generalized contractures and hypotonia. The disorder is caused by a neurogenic defect and poor or absent myelin formation around peripheral nerves rather than by a muscular defect (summary by Xue et al., 2017). <Genetic Heterogeneity of Arthrogryposis Multiplex Congenita Also see AMC2 (208100), caused by mutation in the ERGIC1 gene (617946); AMC3 (618484), caused by mutation in the SYNE1 gene (608441); AMC4 (618776), caused by mutation in the SCYL2 gene (616365); AMC5 (618947), caused by mutation in the TOR1A gene (605204), AMC6 (619334), caused by mutation in the NEB gene (161650), and AMC7 (301127), caused by mutation in the THOC2 gene (300395).

Stankiewicz-Isidor syndrome (STISS) is a neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, behavioral disorders, mild craniofacial anomalies, and variable congenital defects of the cardiac and/or urogenital systems (summary by Kury et al., 2017).

Neurodevelopmental disorder with progressive microcephaly, spasticity, and brain anomalies (NDMSBA) is an autosomal recessive neurodevelopmental disorder characterized by infantile onset of progressive microcephaly and spasticity and severe global developmental delay resulting in profoundly impaired intellectual development and severely impaired or absent motor function. More variable features include seizures and optic atrophy. Brain imaging may show myelinating abnormalities and white matter lesions consistent with a leukoencephalopathy, as well as structural anomalies, including thin corpus callosum, gyral abnormalities, and cerebral or cerebellar atrophy. Some patients die in early childhood (summary by Falik Zaccai et al., 2017 and Hall et al., 2017).

Gabriele-de Vries syndrome is characterized by mild-to-profound developmental delay / intellectual disability (DD/ID) in all affected individuals and a wide spectrum of functional and morphologic abnormalities. Intrauterine growth restriction or low birth weight and feeding difficulties are common. Congenital brain, eye, heart, kidney, genital, and/or skeletal system anomalies have also been reported. About half of affected individuals have neurologic manifestations, including hypotonia and gait abnormalities. Behavioral issues can include attention-deficit/hyperactivity disorder, anxiety, autism or autistic behavior, and schizoaffective disorder.

Galloway-Mowat syndrome is a renal-neurologic disease characterized by early-onset nephrotic syndrome associated with microcephaly, gyral abnormalities of the brain, and delayed psychomotor development. Most patients have dysmorphic facial features, often including hypertelorism, ear abnormalities, and micrognathia. Other features, such as arachnodactyly and visual impairment, are more variable. Most patients die in the first years of life (summary by Braun et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of GAMOS, see GAMOS1 (251300).

WDR26-related intellectual disability (ID) is characterized by developmental delay / intellectual disability, characteristic facial features, hypotonia, epilepsy, and infant feeding difficulties. To date 15 individuals, ages 24 months to 34 years, have been reported. Developmental delay is present in all individuals and ranges from mild to severe. All individuals have delayed speech. Although some begin to develop speech in the second year, others have remained nonverbal. Seizures, present in all affected individuals reported to date, can be febrile or non-febrile (tonic-clonic, absence, rolandic seizures); most seizures are self limited or respond well to standard treatment. Affected individuals are generally described as happy and socially engaging; several have stereotypies / autistic features (repetitive or rocking behavior, abnormal hand movements or posturing, and at times self-stimulation).

Fraser syndrome is an autosomal recessive malformation disorder characterized by cryptophthalmos, syndactyly, and abnormalities of the respiratory and urogenital tract (summary by van Haelst et al., 2008). For a general phenotypic description and a discussion of genetic heterogeneity of Fraser syndrome, see 219000.

Mitochondrial myopathy and ataxia (MMYAT) is an autosomal recessive mtDNA depletion disorder characterized by cerebellar ataxia, congenital muscle involvement with histologic findings ranging from myopathic to dystrophic, and pigmentary retinopathy (summary by Donkervoort et al., 2019).

Developmental and epileptic encephalopathy-91 (DEE91) is characterized by delayed psychomotor development apparent in infancy and resulting in severely to profoundly impaired intellectual development with poor or absent speech. Most patients never achieve independent walking. Patients typically have onset of refractory multifocal seizures between the first weeks and years of life, and some may show developmental regression. Additional features, such as hypotonia and cortical visual impairment, are more variable (summary by Myers et al., 2017). For a discussion of genetic heterogeneity of DEE, see 308350.

Galloway-Mowat syndrome is a renal-neurologic disease characterized by early-onset nephrotic syndrome associated with microcephaly, gyral abnormalities of the brain, and delayed psychomotor development. Most patients have dysmorphic facial features, often including hypertelorism, ear abnormalities, and micrognathia. Other features, such as arachnodactyly and visual impairment, are more variable. Most patients die in the first years of life (summary by Braun et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of GAMOS, see GAMOS1 (251300).

Sweeney-Cox syndrome (SWCOS) is characterized by striking facial dysostosis, including hypertelorism, deficiencies of the eyelids and facial bones, cleft palate/velopharyngeal insufficiency, and low-set cupped ears (Kim et al., 2017).

NEDDFL is a neurodevelopmental disorder characterized by delayed psychomotor development and impaired intellectual development, poor growth with small head size, dysmorphic facial features, and mild abnormalities of the hands and feet (summary by Stankiewicz et al., 2017).

Neurodevelopmental disorder with microcephaly, seizures, and cortical atrophy (NDMSCA) is an autosomal recessive disorder characterized by severe global developmental delay with poor motor and intellectual function apparent soon after birth, as well as postnatal progressive microcephaly. Most patients develop early-onset, frequent, and often intractable seizures, compatible with an epileptic encephalopathy. Other features include poor feeding, poor overall growth, absent speech, poor or absent eye contact, inability to achieve walking, hypotonia, and peripheral spasticity. Brain imaging usually shows progressive cerebral atrophy, thin corpus callosum, and abnormalities in myelination. Death in childhood may occur (summary by Siekierska et al., 2019).

Coffin-Siris syndrome (CSS) is classically characterized by aplasia or hypoplasia of the distal phalanx or nail of the fifth and additional digits, developmental or cognitive delay of varying degree, distinctive facial features, hypotonia, hirsutism/hypertrichosis, and sparse scalp hair. Congenital anomalies can include malformations of the cardiac, gastrointestinal, genitourinary, and/or central nervous systems. Other findings commonly include feeding difficulties, slow growth, ophthalmologic abnormalities, and hearing impairment.

Seckel syndrome is a rare autosomal recessive disorder characterized by intrauterine growth retardation, dwarfism, microcephaly with mental retardation, and a characteristic 'bird-headed' facial appearance (Shanske et al., 1997). Genetic Heterogeneity of Seckel Syndrome Other forms of Seckel syndrome include SCKL2 (606744), caused by mutation in the RBBP8 gene (604124) on chromosome 18q11; SCKL4 (613676), caused by mutation in the CENPJ gene (609279) on chromosome 13q12; SCKL5 (613823), caused by mutation in the CEP152 gene (613529) on chromosome 15q21; SCKL6 (614728), caused by mutation in the CEP63 gene (614724) on chromosome 3q22; SCKL7 (614851), caused by mutation in the NIN gene (608684) on chromosome 14q22; SCKL8 (615807), caused by mutation in the DNA2 gene (601810) on chromosome 10q21; SCKL9 (616777), caused by mutation in the TRAIP gene (605958) on chromosome 3p21; SCKL10 (617253), caused by mutation in the NSMCE2 gene (617246) on chromosome 8q24; and SCKL11 (620767), caused by mutation in the CEP295 gene (617728) on chromosome 11q21. The report of a Seckel syndrome locus on chromosome 14q, designated SCKL3, by Kilinc et al. (2003) was found to be in error; see History section.

Autosomal dominant Robinow syndrome (ADRS) is characterized by skeletal findings (short stature, mesomelic limb shortening predominantly of the upper limbs, and brachydactyly), genital abnormalities (in males: micropenis / webbed penis, hypoplastic scrotum, cryptorchidism; in females: hypoplastic clitoris and labia majora), dysmorphic facial features (widely spaced and prominent eyes, frontal bossing, anteverted nares, midface retrusion), dental abnormalities (including malocclusion, crowding, hypodontia, late eruption of permanent teeth), bilobed tongue, and occasional prenatal macrocephaly that persists postnatally. Less common findings include renal anomalies, radial head dislocation, vertebral abnormalities such as hemivertebrae and scoliosis, nail dysplasia, cardiac defects, cleft lip/palate, and (rarely) cognitive delay. When present, cardiac defects are a major cause of morbidity and mortality. A variant of Robinow syndrome, associated with osteosclerosis and caused by a heterozygous pathogenic variant in DVL1, is characterized by normal stature, persistent macrocephaly, increased bone mineral density with skull osteosclerosis, and hearing loss, in addition to the typical features described above.

Any Neu-Laxova syndrome in which the cause of the disease is a mutation in the PHGDH gene.

Schwartz-Jampel syndrome type 1 (SJS1) is a rare autosomal recessive disorder characterized by muscle stiffness (myotonia) and chondrodysplasia. Affected individuals usually present in childhood with permanent muscle stiffness or bone deformities. Common clinical features include mask-like facies (narrow palpebral fissures, blepharospasm, and pursed lips); permanent muscle stiffness with continuous skeletal muscle activity recorded on electromyography; dwarfism; pectus carinatum; kyphoscoliosis; bowing of long bones; and epiphyseal, metaphyseal, and hip dysplasia. The disorder is slowly progressive but does not appear to alter life span (summary by Stum et al., 2006).

Carpenter syndrome is a rare autosomal recessive disorder with the cardinal features of acrocephaly with variable synostosis of the sagittal, lambdoid, and coronal sutures; peculiar facies; brachydactyly of the hands with syndactyly; preaxial polydactyly and syndactyly of the feet; congenital heart defects; growth retardation; mental retardation; hypogenitalism; and obesity. In addition, cerebral malformations, oral and dental abnormalities, coxa valga, genu valgum, hydronephrosis, precocious puberty, and hearing loss may be observed (summary by Altunhan et al., 2011). Genetic Heterogeneity of Carpenter Syndrome Carpenter syndrome-2 (CRPT2; 614976), in which the features of Carpenter syndrome are sometimes associated with defective lateralization, is caused by mutation in the MEGF8 gene (604267).

Immunodeficiency, centromeric instability, and facial dysmorphism (ICF) syndrome is a rare autosomal recessive disease characterized by facial dysmorphism, immunoglobulin deficiency, and branching of chromosomes 1, 9, and 16 after phytohemagglutinin (PHA) stimulation of lymphocytes. Hypomethylation of DNA of a small fraction of the genome is an unusual feature of ICF patients that is explained by mutations in the DNMT3B gene in some, but not all, ICF patients (Hagleitner et al., 2008). Genetic Heterogeneity of Immunodeficiency-Centromeric Instability-Facial Anomalies Syndrome See also ICF2 (614069), caused by mutation in the ZBTB24 gene (614064) on chromosome 6q21; ICF3 (616910), caused by mutation in the CDCA7 gene (609937) on chromosome 2q31; and ICF4 (616911), caused by mutation in the HELLS gene (603946) on chromosome 10q23.