Apert syndrome is characterized by the presence of multisuture craniosynostosis, midface retrusion, and syndactyly of the hands with fusion of the second through fourth nails. Almost all affected individuals have coronal craniosynostosis, and a majority also have involvement of the sagittal and lambdoid sutures. The midface in Apert syndrome is underdeveloped as well as retruded; a subset of affected individuals have cleft palate. The hand in Apert syndrome always includes fusion of the middle three digits; the thumb and fifth finger are sometimes also involved. Feeding issues, dental abnormalities, hearing loss, hyperhidrosis, and progressive synostosis of multiple bones (skull, hands, feet, carpus, tarsus, and cervical vertebrae) are also common. Multilevel airway obstruction may be present and can be due to narrowing of the nasal passages, tongue-based airway obstruction, and/or tracheal anomalies. Nonprogressive ventriculomegaly is present in a majority of individuals, with a small subset having true hydrocephalus. Most individuals with Apert syndrome have normal intelligence or mild intellectual disability; moderate-to-severe intellectual disability has been reported in some individuals. A minority of affected individuals have structural cardiac abnormalities, true gastrointestinal malformations, and anomalies of the genitourinary tract.

Beckwith-Wiedemann syndrome (BWS) is a growth disorder variably characterized by neonatal hypoglycemia, macrosomia, macroglossia, hemihyperplasia, omphalocele, embryonal tumors (e.g., Wilms tumor, hepatoblastoma, neuroblastoma, and rhabdomyosarcoma), visceromegaly, adrenocortical cytomegaly, renal abnormalities (e.g., medullary dysplasia, nephrocalcinosis, medullary sponge kidney, and nephromegaly), and ear creases/pits. BWS is considered a clinical spectrum, in which affected individuals may have many of these features or may have only one or two clinical features. Early death may occur from complications of prematurity, hypoglycemia, cardiomyopathy, macroglossia, or tumors. However, the previously reported mortality of 20% is likely an overestimate given better recognition of the disorder along with enhanced treatment options. Macroglossia and macrosomia are generally present at birth but may have postnatal onset. Growth rate slows around age seven to eight years. Hemihyperplasia may affect segmental regions of the body or selected organs and tissues.

Cherubism is a childhood-onset, autoinflammatory bone disease characterized by bilateral and symmetric proliferative fibroosseous lesions limited to the mandible and maxilla. The enlargement is usually symmetric in nature. The phenotype ranges from no clinical manifestations to severe mandibular and maxillary overgrowth with respiratory, vision, speech, and swallowing problems. In most affected persons, teeth are displaced, unerupted, unformed, or absent, or may appear to be floating in cystlike spaces; malocclusion, premature exfoliation of deciduous teeth, and root resorption have also been reported. The course and duration of the active process of bone destruction varies between affected individuals; the onset is usually in early childhood, and typically new lesions can occur until puberty. Regression of the lesions occurs as they become filled with bone and remodel during the second and third decade of life. By age 30 years, the facial abnormalities associated with cherubism are not usually recognizable and residual deformity of the jaws is rare. Typically, cherubism is an isolated benign condition; the affected person has normal intellectual skills and is without other physical anomalies.

Crouzon syndrome is an autosomal dominant disorder characterized by craniosynostosis causing secondary alterations of the facial bones and facial structure. Common features include hypertelorism, exophthalmos and external strabismus, parrot-beaked nose, short upper lip, hypoplastic maxilla, and a relative mandibular prognathism (Reardon et al., 1994; Glaser et al., 2000).

Camurati-Engelmann disease (CED) is characterized by hyperostosis of the long bones and the skull, proximal muscle weakness, limb pain, a wide-based, waddling gait, and joint contractures. Facial features such as macrocephaly, frontal bossing, enlargement of the mandible, proptosis, and cranial nerve impingement resulting in facial palsy are seen in severely affected individuals later in life.

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is characterized by progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy and generalized areflexia, progressive external ophthalmoplegia, action-induced facial and lingual fasciculations, and bulging eyes. Neurologic findings tend to evolve as the disorder progresses.

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.

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.

People with CCHD have one or more specific heart defects. The heart defects classified as CCHD include coarctation of the aorta, double-outlet right ventricle, D-transposition of the great arteries, Ebstein anomaly, hypoplastic left heart syndrome, interrupted aortic arch, pulmonary atresia with intact septum, single ventricle, total anomalous pulmonary venous connection, tetralogy of Fallot, tricuspid atresia, and truncus arteriosus.\n\nEach of the heart defects associated with CCHD affects the flow of blood into, out of, or through the heart. Some of the heart defects involve structures within the heart itself, such as the two lower chambers of the heart (the ventricles) or the valves that control blood flow through the heart. Others affect the structure of the large blood vessels leading into and out of the heart (including the aorta and pulmonary artery). Still others involve a combination of these structural abnormalities.\n\nSome people with treated CCHD have few related health problems later in life. However, long-term effects of CCHD can include delayed development and reduced stamina during exercise. Adults with these heart defects have an increased risk of abnormal heart rhythms, heart failure, sudden cardiac arrest, stroke, and premature death.\n\nAlthough babies with CCHD may appear healthy for the first few hours or days of life, signs and symptoms soon become apparent. These can include an abnormal heart sound during a heartbeat (heart murmur), rapid breathing (tachypnea), low blood pressure (hypotension), low levels of oxygen in the blood (hypoxemia), and a blue or purple tint to the skin caused by a shortage of oxygen (cyanosis). If untreated, CCHD can lead to shock, coma, and death. However, most people with CCHD now survive past infancy due to improvements in early detection, diagnosis, and treatment.\n\nCritical congenital heart disease (CCHD) is a term that refers to a group of serious heart defects that are present from birth. These abnormalities result from problems with the formation of one or more parts of the heart during the early stages of embryonic development. CCHD prevents the heart from pumping blood effectively or reduces the amount of oxygen in the blood. As a result, organs and tissues throughout the body do not receive enough oxygen, which can lead to organ damage and life-threatening complications. Individuals with CCHD usually require surgery soon after birth.

Hypophosphatasia is characterized by defective mineralization of growing or remodeling bone, with or without root-intact tooth loss, in the presence of low activity of serum and bone alkaline phosphatase. Clinical features range from stillbirth without mineralized bone at the severe end to pathologic fractures of the lower extremities in later adulthood at the mild end. While the disease spectrum is a continuum, seven clinical forms of hypophosphatasia are usually recognized based on age at diagnosis and severity of features: Perinatal (severe): characterized by pulmonary insufficiency and hypercalcemia. Perinatal (benign): prenatal skeletal manifestations that slowly resolve into one of the milder forms. Infantile: onset between birth and age six months of clinical features of rickets without elevated serum alkaline phosphatase activity. Severe childhood (juvenile): variable presenting features progressing to rickets. Mild childhood: low bone mineral density for age, increased risk of fracture, and premature loss of primary teeth with intact roots. Adult: characterized by stress fractures and pseudofractures of the lower extremities in middle age, sometimes associated with early loss of adult dentition. Odontohypophosphatasia: characterized by premature exfoliation of primary teeth and/or severe dental caries without skeletal manifestations.

The Marshall-Smith syndrome (MRSHSS) is a malformation syndrome characterized by accelerated skeletal maturation, relative failure to thrive, respiratory difficulties, mental retardation, and unusual facies, including prominent forehead, shallow orbits, blue sclerae, depressed nasal bridge, and micrognathia (Adam et al., 2005).

Kniest dysplasia is characterized by skeletal and craniofacial anomalies. Skeletal anomalies include disproportionate dwarfism, a short trunk and small pelvis, kyphoscoliosis, short limbs, and prominent joints and premature osteoarthritis that restrict movement. Craniofacial manifestations include midface hypoplasia, cleft palate, early-onset myopia, retinal detachment, and hearing loss. The phenotype is severe in some patients and mild in others. There are distinct radiographic changes including coronal clefts of vertebrae and dumbbell-shaped femora. The chondrooseous morphology is pathognomonic with perilacunar 'foaminess' and sparse, aggregated collagen fibrils resulting in an interterritorial matrix with a 'Swiss-cheese' appearance (summary by Wilkin et al., 1999).

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).

INSR-related severe syndromic insulin resistance comprises a phenotypic spectrum that is a continuum from the severe phenotype Donohue syndrome (DS) (also known as leprechaunism) to the milder phenotype Rabson-Mendenhall syndrome (RMS). DS at the severe end of the spectrum is characterized by severe insulin resistance (hyperinsulinemia with associated fasting hypoglycemia and postprandial hyperglycemia), severe prenatal growth restriction and postnatal growth failure, hypotonia and developmental delay, characteristic facies, and organomegaly involving heart, kidneys, liver, spleen, and ovaries. Death usually occurs before age one year. RMS at the milder end of the spectrum is characterized by severe insulin resistance that, although not as severe as that of DS, is nonetheless accompanied by fluctuations in blood glucose levels, diabetic ketoacidosis, and – in the second decade – microvascular complications. Findings can range from severe growth delay and intellectual disability to normal growth and development. Facial features can be milder than those of DS. Complications of longstanding hyperglycemia are the most common cause of death. While death usually occurs in the second decade, some affected individuals live longer.

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).

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.

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.

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).

Chronic infantile neurologic cutaneous and articular syndrome (CINCA) is an early-onset, severe, chronic inflammatory disease, characterized by cutaneous symptoms, central nervous system involvement, and arthropathy (Feldmann et al., 2002). See also familial cold autoinflammatory syndrome-1 (FCAS1, CAPS1; 120100), an allelic disorder with a less severe phenotype.

Cloverleaf skull, or Kleeblattschaedel, consists of a trilobular skull with craniosynostosis. The condition shows pathogenetic variability and etiologic heterogeneity. The cause of isolated cloverleaf skull is unknown (Cohen, 2009). Cohen (1975) pointed out that Kleeblattschaedel is a component of many syndromes, e.g., it is found in some cases of Crouzon syndrome (123500), Pfeiffer syndrome (101600), and Carpenter syndrome (201000). Cohen (2009) listed 12 monogenic disorders with cloverleaf skull as a feature, including type II thanatophoric dysplasia (187601), which accounts for 40% of all cloverleaf skull syndromes. Cohen (2009) published photographs of cloverleaf skull in various syndromes.

Opsismodysplasia (OPSMD) is a rare skeletal dysplasia involving delayed bone maturation. Clinical signs observed at birth include short limbs, small hands and feet, relative macrocephaly with a large anterior fontanel, and characteristic craniofacial abnormalities including a prominent brow, depressed nasal bridge, a small anteverted nose, and a relatively long philtrum. Death in utero or secondary to respiratory failure during the first few years of life has been reported, but there can be long-term survival. Typical radiographic findings include shortened long bones with delayed epiphyseal ossification, severe platyspondyly, metaphyseal cupping, and characteristic abnormalities of the metacarpals and phalanges (summary by Below et al., 2013 and Fradet and Fitzgerald, 2017).

Osteoglophonic dysplasia (OGD) is characterized by rhizomelic dwarfism, nonossifying bone lesions, craniosynostosis, prominent supraorbital ridge, and depressed nasal bridge (summary by White et al., 2005).

Autosomal recessive congenital ichthyosis (ARCI) encompasses several forms of nonsyndromic ichthyosis. Although most neonates with ARCI are collodion babies, the clinical presentation and severity of ARCI may vary significantly, ranging from harlequin ichthyosis, the most severe and often fatal form, to lamellar ichthyosis (LI) and (nonbullous) congenital ichthyosiform erythroderma (CIE). These phenotypes are now recognized to fall on a continuum; however, the phenotypic descriptions are clinically useful for clarification of prognosis and management. Infants with harlequin ichthyosis are usually born prematurely and are encased in thick, hard, armor-like plates of cornified skin that severely restrict movement. Life-threatening complications in the immediate postnatal period include respiratory distress, feeding problems, and systemic infection. Collodion babies are born with a taut, shiny, translucent or opaque membrane that encases the entire body and lasts for days to weeks. LI and CIE are seemingly distinct phenotypes: classic, severe LI with dark brown, plate-like scale with no erythroderma and CIE with finer whiter scale and underlying generalized redness of the skin. Affected individuals with severe involvement can have ectropion, eclabium, scarring alopecia involving the scalp and eyebrows, and palmar and plantar keratoderma. Besides these major forms of nonsyndromic ichthyosis, a few rare subtypes have been recognized, such as bathing suit ichthyosis, self-improving collodion ichthyosis, or ichthyosis-prematurity syndrome.

Filippi syndrome is characterized by short stature, microcephaly, syndactyly, intellectual disability, and facial dysmorphism consisting of bulging forehead, broad and prominent nasal bridge, and diminished alar flare. Common features include cryptorchidism, speech impairment, and clinodactyly of the fifth finger, Some patients exhibit visual disturbances, polydactyly, seizures, and/or ectodermal abnormalities, such as nail hypoplasia, long eyelashes, hirsutism, and microdontia (summary by Hussain et al., 2014).

Jackson-Weiss syndrome (JWS) is an autosomal dominant condition consisting of craniosynostosis characterized by premature fusion of the cranial sutures as well as radiographic anomalies of the feet (summary by Heike et al., 2001).

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.

The core phenotype of Elsahy-Waters syndrome consists of brachycephaly, facial asymmetry, marked hypertelorism, proptosis, blepharochalasis, midface hypoplasia, broad nose with concave nasal ridge, and prognathism; radicular dentin dysplasia with consequent obliterated pulp chambers, apical translucent cysts, recurrent infections, and early loss of teeth; vertebral fusions, particularly at C2-C3; and moderate mental retardation. Skin wrinkling over the glabellar region seems common, and in males, hypospadias has always been present. Inter- and intrafamilial variability has been reported regarding the presence of vertebral fusions, hearing loss, and dentigerous cysts. Midface hypoplasia, facial asymmetry, progressive dental anomalies, and impaired cognitive development become more evident in adulthood (summary by Castori et al., 2010).

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.

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.

Craniosynostosis (CRS) is a primary abnormality of skull growth involving premature fusion of the cranial sutures such that the growth velocity of the skull often cannot match that of the developing brain. This produces skull deformity and, in some cases, raises intracranial pressure, which must be treated promptly to avoid permanent neurodevelopmental disability (summary by Fitzpatrick, 2013). Craniosynostosis-4 (CRS4) includes lambdoid, sagittal, metopic, coronal, and multisuture forms. For a discussion of genetic heterogeneity of craniosynostosis, see CRS1 (123100).

A rare disorder characterized by the partial separation of the cerebral hemispheres. It is associated with mutations in the SIX3 gene.

A rare hyperthyroidism characterized by mild to severe hyperthyroidism, presence of goiter, absence of features of autoimmunity, frequent relapses while on treatment and a positive family history.

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.

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).

Oculoectodermal syndrome (OES) is characterized by the association of epibulbar dermoids and aplasia cutis congenita. Affected individuals exhibit congenital scalp lesions which are atrophic, nonscarring, hairless regions that are often multiple and asymmetric in distribution, and may have associated hamartomas. Ectodermal changes include linear hyperpigmentation that may follow the lines of Blaschko and, rarely, epidermal nevus-like lesions. Epibulbar dermoids may be uni- or bilateral. Additional ocular anomalies such as skin tags of the upper eyelid and rarely optic nerve or retinal changes or microphthalmia can be present. Phenotypic expression is highly variable, and various other abnormalities have occasionally been reported, including growth failure, lymphedema, and cardiovascular defects, as well as neurodevelopmental symptoms such as developmental delay, epilepsy, learning difficulties, and behavioral abnormalities. Benign tumor-like lesions such as nonossifying fibromas of the long bones and giant cell granulomas of the jaws have repeatedly been observed and appear to be age-dependent, becoming a common manifestation in individuals aged 5 years or older (summary by Boppudi et al., 2016).

Hyperostosis cranialis interna (HCIN) is a bone disorder characterized by endosteal hyperostosis and osteosclerosis of the calvaria and the skull base. The progressive bone overgrowth causes entrapment and dysfunction of cranial nerves I, II, V, VII, and VIII (Waterval et al., 2010).

Any holoprosencephaly in which the cause of the disease is a mutation in the SHH gene.

Pontocerebellar hypoplasia (PCH) refers to a heterogeneous group of disorders characterized by an abnormally small cerebellum and brainstem. Clinical features vary, but usually include severe developmental delay, dysmorphic features, seizures, and early death (summary by Durmaz et al., 2009). For a phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1 (607596).

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).

Primary intraosseous vascular malformation (VMPI), previously called intraosseous hemangioma, is a rare malformation that usually involves the vertebral column and the skull. The most commonly affected bones in the skull are the mandible and the maxilla, and life-threatening bleeding after a simple tooth extraction is frequent (Vargel et al., 2002).

Graves disease (GRD) is an autoimmune disorder in which antibodies to the thyrotropin receptor (TSHR; 603372) result in constitutive activation of the receptor and increased levels of thyroid hormone. Wilkin (1990) reviewed endocrine disorders of hormone excess and hormone deficiency resulting from receptor autoimmunity. Genetic Heterogeneity of Graves Disease Susceptibility to Graves disease-1 (GRD1) has been mapped to chromosome 14q31. Other susceptibility loci for Graves disease include GRD2 (603388) on chromosome 20q13, GRDX1 (300351) on Xp11, and GRDX2 (see 300351) on Xq21.33-q22. Graves disease has also been mapped to several loci that confer susceptibility to autoimmune thyroid diseases, including Hashimoto thyroiditis (HT; 140300): AITD1 (608173) on 6p11; AITD2 (608174) on 5q31-q33; AITD3 (608175) on 8q24; AITD4 (608176) on 10q, and AITD5 (601941) on 18q21.

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).

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).

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).

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized clinically by bone fragility and increased susceptibility to fractures. Osteogenesis imperfecta type IX (OI9) is a severe autosomal recessive form of the disorder (summary by van Dijk et al., 2009).

Beare-Stevenson cutis gyrata syndrome (BSTVS) is an autosomal dominant condition characterized by the furrowed skin disorder of cutis gyrata, acanthosis nigricans, craniosynostosis, craniofacial dysmorphism, digital anomalies, umbilical and anogenital abnormalities, and early death (summary by Przylepa et al., 1996).

Osteogenesis imperfecta is a connective tissue disorder characterized by bone fragility and low bone mass. OI type VII is an autosomal recessive form of severe or lethal OI (summary by Barnes et al., 2006).

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).

A very rare syndrome associating an acro-fronto-facio-nasal dysostosis with genitourinary anomalies. It has been described in three families. Craniofacial manifestations include wide anterior fontanelle, flat occiput, hypertelorism, ptosis, proptosis, broad nasal bridge and nasal tip, long philtrum and posteriorly rotated or low set ears. Hypospadias and shawl scrotum are present in all males. Acral manifestations include syndactyly of fingers, broad thumbs or halluces or preaxial polydactyly. The affected patients have no intellectual deficit. The condition seems to be hereditary, and transmitted as an autosomal recessive trait.

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.

Donnai-Barrow syndrome (DBS) is characterized by typical craniofacial features (large anterior fontanelle, wide metopic suture, widow's peak, markedly widely spaced eyes, enlarged globes, downslanted palpebral fissures, posteriorly rotated ears, depressed nasal bridge, and short nose. Ocular complications include high myopia, retinal detachment, retinal dystrophy, and progressive vision loss. Additional common features include agenesis of the corpus callosum, sensorineural hearing loss, intellectual disability, and congenital diaphragmatic hernia and/or omphalocele. Both inter- and intrafamilial phenotypic variability are observed.

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).

Microhydranencephaly (MHAC) is a severe neurodevelopmental defect characterized by extreme microcephaly, profound motor and mental retardation, spasticity, and incomplete cerebral formation. Radiologic studies show gross dilation of the ventricles resulting from the absence of cerebral hemispheres or severe delay in their development, as well as hypoplasia of the corpus callosum, cerebellum, and brainstem (summary by Guven et al., 2012).

People with MCPH usually have few or no other features associated with the condition. Some have a narrow, sloping forehead; mild seizures; problems with attention or behavior; or short stature compared to others in their family. The condition typically does not affect any other major organ systems or cause other health problems.\n\nInfants with MCPH have an unusually small head circumference compared to other infants of the same sex and age. Head circumference is the distance around the widest part of the head, measured by placing a measuring tape above the eyebrows and ears and around the back of the head. Affected infants' brain volume is also smaller than usual, although they usually do not have any major abnormalities in the structure of the brain. The head and brain grow throughout childhood and adolescence, but they continue to be much smaller than normal.\n\nMCPH causes intellectual disability, which is typically mild to moderate and does not become more severe with age. Most affected individuals have delayed speech and language skills. Motor skills, such as sitting, standing, and walking, may also be mildly delayed.\n\nAutosomal recessive primary microcephaly (often shortened to MCPH, which stands for "microcephaly primary hereditary") is a condition in which infants are born with a very small head and a small brain. The term "microcephaly" comes from the Greek words for "small head."

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).

Muenke syndrome is defined by the presence of the specific FGFR3 pathogenic variant – c.749C>G – that results in the protein change p.Pro250Arg. Muenke syndrome is characterized by considerable phenotypic variability: features may include coronal synostosis (more often bilateral than unilateral); synostosis of other sutures, all sutures (pan synostosis), or no sutures; or macrocephaly. Bilateral coronal synostosis typically results in brachycephaly (reduced anteroposterior dimension of the skull), although turribrachycephaly (a "tower-shaped" skull) or a cloverleaf skull can be observed. Unilateral coronal synostosis results in anterior plagiocephaly (asymmetry of the skull and face). Other craniofacial findings typically include: temporal bossing; widely spaced eyes, ptosis or proptosis (usually mild); midface retrusion (usually mild); and highly arched palate or cleft lip and palate. Strabismus is common. Other findings can include: hearing loss (in 33%-100% of affected individuals); developmental delay (~33%); epilepsy; intracranial anomalies; intellectual disability; carpal bone and/or tarsal bone fusions; brachydactyly, broad toes, broad thumbs, and/or clinodactyly; and radiographic findings of thimble-like (short and broad) middle phalanges and/or cone-shaped epiphyses. Phenotypic variability is considerable even within the same family. Of note, some individuals who have the p.Pro250Arg pathogenic variant may have no signs of Muenke syndrome on physical or radiographic examination.

The histiocytosis-lymphadenopathy plus syndrome comprises features of 4 histiocytic disorders previously thought to be distinct: Faisalabad histiocytosis (FHC), sinus histiocytosis with massive lymphadenopathy (SHML), H syndrome, and pigmented hypertrichosis with insulin-dependent diabetes mellitus syndrome (PHID). FHC was described as an autosomal recessive disease involving joint deformities, sensorineural hearing loss, and subsequent development of generalized lymphadenopathy and swellings in the eyelids that contain histiocytes (summary by Morgan et al., 2010). SHML, or familial Rosai-Dorfman disease, was described as a rare cause of lymph node enlargement in children, consisting of chronic massive enlargement of cervical lymph nodes frequently accompanied by fever, leukocytosis, elevated erythrocyte sedimentation rate, and polyclonal hypergammaglobulinemia. Extranodal sites were involved in approximately 25% of patients, including salivary glands, orbit, eyelid, spleen, and testes. The involvement of retropharyngeal lymphoid tissue sometimes caused snoring and sleep apnea (summary by Kismet et al., 2005). H syndrome was characterized by cutaneous hyperpigmentation and hypertrichosis, hepatosplenomegaly, heart anomalies, and hypogonadism; hearing loss was also found in about half of patients, and many had short stature. PHID was characterized by predominantly antibody-negative insulin-dependent diabetes mellitus associated with pigmented hypertrichosis and variable occurrence of other features of H syndrome, with hepatosplenomegaly occurring in about half of patients (Cliffe et al., 2009). Bolze et al. (2012) noted that mutations in the SLC29A3 gene (612373) had been implicated in H syndrome, PHID, FHC, and SHML, and that some patients presented a combination of features from 2 or more of these syndromes, leading to the suggestion that these phenotypes should be grouped together as 'SLC29A3 disorder.' Bolze et al. (2012) suggested that the histologic features of the lesions seemed to be the most uniform phenotype in these patients. In addition, the immunophenotype of infiltrating cells in H syndrome patients was shown to be the same as that seen in patients with the familial form of Rosai-Dorfman disease, further supporting the relationship between these disorders (Avitan-Hersh et al., 2011; Colmenero et al., 2012).

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).

Holoprosencephaly associated with mutations in the ZIC2 gene.

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).

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).

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized by bone fragility and low bone mass. Due to considerable phenotypic variability, Sillence et al. (1979) developed a classification of OI subtypes based on clinical features and disease severity: OI type I, with blue sclerae (166200); perinatal lethal OI type II, also known as congenital OI (166210); OI type III, a progressively deforming form with normal sclerae (259420); and OI type IV, with normal sclerae (166220). Most forms of OI are autosomal dominant with mutations in one of the 2 genes that code for type I collagen alpha chains, COL1A1 (120150) and COL1A2 (120160). Cabral et al. (2007) described a form of autosomal recessive OI, which they designated OI type VIII, characterized by white sclerae, severe growth deficiency, extreme skeletal undermineralization, and bulbous metaphyses.

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.

Autosomal recessive osteopetrosis-7 (OPTB7) is an osteoclast-poor form of osteopetrosis with hypogammaglobulinemia. Clinical features include visual impairment, recurrent respiratory infections, poor growth, developmental delay, and increased bone density (Guerrini et al., 2008). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal recessive osteopetrosis, see OPTB1 (259700).

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.

Crouzon syndrome with acanthosis nigricans is considered to be a distinct disorder from classic Crouzon syndrome (123500), which is caused by mutation in the FGFR2 gene (176943). Cohen (1999) argued that this condition is separate from Crouzon syndrome for 2 main reasons: it is caused by a highly specific mutation of the FGFR3 gene, whereas multiple different FGFR2 mutations result in Crouzon syndrome, and the phenotypes are different.

Axenfeld-Rieger syndrome is primarily an eye disorder, although it can also affect other parts of the body. This condition is characterized by abnormalities of the front part of the eye, an area known as the anterior segment. For example, the colored part of the eye (the iris), may be thin or poorly developed. The iris normally has a single central hole, called the pupil, through which light enters the eye. People with Axenfeld-Rieger syndrome often have a pupil that is off-center (corectopia) or extra holes in the iris that can look like multiple pupils (polycoria). This condition can also cause abnormalities of the cornea, which is the clear front covering of the eye.\n\nAbout half of affected individuals develop glaucoma, a serious condition that increases pressure inside the eye. When glaucoma occurs with Axenfeld-Rieger syndrome, it most often develops in late childhood or adolescence, although it can occur as early as infancy. Glaucoma can cause vision loss or blindness.\n\nThe signs and symptoms of Axenfeld-Rieger syndrome can also affect other parts of the body. Many affected individuals have distinctive facial features such as widely spaced eyes (hypertelorism); a flattened mid-face with a broad, flat nasal bridge; and a prominent forehead. The condition is also associated with dental abnormalities including unusually small teeth (microdontia) or fewer than normal teeth (oligodontia). Some people with Axenfeld-Rieger syndrome have extra folds of skin around their belly button (redundant periumbilical skin). Other, less common features can include heart defects, the opening of the urethra on the underside of the penis (hypospadias), narrowing of the anus (anal stenosis), and abnormalities of the pituitary gland that can result in slow growth.\n\nResearchers have described at least three types of Axenfeld-Rieger syndrome. The types, which are numbered 1 through 3, are distinguished by their genetic cause.

A rare partial autosomal trisomy/tetrasomy characterized by global developmental delay, intellectual disability, autistic behavior, muscular hypotonia, macrocephaly and facial dysmorphism (frontal bossing, short palpebral fissures, low set, dysplastic ears, short or shallow philtrum, high arched or narrow palate, micrognathia). Other associated clinical features include sleep disturbances, seizures, aplasia/hypoplasia of the corpus callosum, skeletal abnormalities (large hands and feet, long fingers and toes, talipes).

Any multiple synostoses syndrome in which the cause of the disease is a mutation in the FGF9 gene.

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.

Cytochrome P450 oxidoreductase deficiency (PORD) is a disorder of steroidogenesis with a broad phenotypic spectrum including cortisol deficiency, altered sex steroid synthesis, disorders of sex development (DSD), and skeletal malformations of the Antley-Bixler syndrome (ABS) phenotype. Cortisol deficiency is usually partial, with some baseline cortisol production but failure to mount an adequate cortisol response in stress. Mild mineralocorticoid excess can be present and causes arterial hypertension, usually presenting in young adulthood. Manifestations of altered sex steroid synthesis include ambiguous genitalia/DSD in both males and females, large ovarian cysts in females, poor masculinization and delayed puberty in males, and maternal virilization during pregnancy with an affected fetus. Skeletal malformations can manifest as craniosynostosis, mid-face retrusion with proptosis and choanal stenosis or atresia, low-set dysplastic ears with stenotic external auditory canals, hydrocephalus, radiohumeral synostosis, neonatal fractures, congenital bowing of the long bones, joint contractures, arachnodactyly, and clubfeet; other anomalies observed include urinary tract anomalies (renal pelvic dilatation, vesicoureteral reflux). Cognitive impairment is of minor concern and likely associated with the severity of malformations; studies of developmental outcomes are lacking.

Cytochrome P450 oxidoreductase deficiency (PORD) is a disorder of steroidogenesis with a broad phenotypic spectrum including cortisol deficiency, altered sex steroid synthesis, disorders of sex development (DSD), and skeletal malformations of the Antley-Bixler syndrome (ABS) phenotype. Cortisol deficiency is usually partial, with some baseline cortisol production but failure to mount an adequate cortisol response in stress. Mild mineralocorticoid excess can be present and causes arterial hypertension, usually presenting in young adulthood. Manifestations of altered sex steroid synthesis include ambiguous genitalia/DSD in both males and females, large ovarian cysts in females, poor masculinization and delayed puberty in males, and maternal virilization during pregnancy with an affected fetus. Skeletal malformations can manifest as craniosynostosis, mid-face retrusion with proptosis and choanal stenosis or atresia, low-set dysplastic ears with stenotic external auditory canals, hydrocephalus, radiohumeral synostosis, neonatal fractures, congenital bowing of the long bones, joint contractures, arachnodactyly, and clubfeet; other anomalies observed include urinary tract anomalies (renal pelvic dilatation, vesicoureteral reflux). Cognitive impairment is of minor concern and likely associated with the severity of malformations; studies of developmental outcomes are lacking.

Syndromic multisystem autoimmune disease due to Itch deficiency is a rare, genetic, systemic autoimmune disease characterized by failure to thrive, global developmental delay, distinctive craniofacial dysmorphism (relative macrocephaly, dolichocephaly, frontal bossing, orbital proptosis, flattened midface with a prominent occiput, low, posteriorly rotated ears, micrognatia), hepato- and/or splenomegaly, and multisystemic autoimmune disease involving the lungs, liver, gut and/or thyroid gland.

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.

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).

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).

Fibrochondrogenesis is a severe, autosomal recessive, short-limbed skeletal dysplasia clinically characterized by a flat midface with a small nose and anteverted nares, significant shortening of all limb segments but relatively normal hands and feet, and a small bell-shaped thorax with a protuberant abdomen. Radiographically, the long bones are short and have broad metaphyseal ends, giving them a dumb-bell shape. The vertebral bodies are flat and, on lateral view, have a distinctive pinched appearance, with a hypoplastic posterior end and a rounded anterior end. The ribs are typically short and wide and have metaphyseal cupping at both ends (summary by Tompson et al., 2010). Genetic Heterogeneity of Fibrochondrogenesis Fibrochondrogenesis-2 (FBCG2; 614524) is caused by mutation in the COL11A2 gene (120290) on chromosome 6p21.3.

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).

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).

CRSDA is an autosomal recessive disorder characterized by craniosynostosis, maxillary hypoplasia, and dental anomalies, including malocclusion, delayed and ectopic tooth eruption, and/or supernumerary teeth. Some patients also display minor digit anomalies, such as syndactyly and/or clinodactyly (summary by Nieminen et al., 2011).

Any holoprosencephaly in which the cause of the disease is a mutation in the CDON gene.

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.

A rare, autosomal recessive inherited disorder usually caused by mutations in the THRB gene. It is characterized by a defective physiological resistance to thyroid hormones, resulting in the elevation of thyroxin and triiodothyronine in the serum.

Among the Yakuts, an Asian population isolate that is located in the northeastern part of Siberia, Maksimova et al. (2010) ascertained an autosomal recessive short stature syndrome involving postnatal growth failure, small hands and feet, loss of visual acuity with abnormalities of color vision, abnormal nuclear shape in neutrophil granulocytes (Pelger-Huet anomaly; see 169400), and normal intelligence.

A rare multiple congenital anomalies syndrome with characteristics of distinctive facial appearance (low frontal hairline, bilateral ptosis, prominent eyes, flat midface, broad, ?at nares, Cupid''s bow upper lip vermilion and small, low-set, posteriorly rotated ears), cleft palate, conductive hearing loss, heart defects (atrial or ventricular septal defect) and mild developmental delay/intellectual disability.

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.

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.

Desbuquois dysplasia (DBQD) is an autosomal recessive chondrodysplasia belonging to the multiple dislocation group and characterized by severe prenatal and postnatal growth retardation (stature less than -5 SD), joint laxity, short extremities, and progressive scoliosis. The main radiologic features are short long bones with metaphyseal splay, a 'Swedish key' appearance of the proximal femur (exaggerated trochanter), and advanced carpal and tarsal bone age with a delta phalanx (summary by Huber et al., 2009). Desbuquois dysplasia is clinically and radiographically heterogeneous, and had been classified into 2 types based on the presence (type 1) or absence (type 2) of characteristic hand anomalies, including an extra ossification center distal to the second metacarpal, delta phalanx, bifid distal thumb phalanx, and dislocation of the interphalangeal joints (Faivre et al., 2004). However, patients with and without these additional hand anomalies have been reported to have mutations in the same gene (see, e.g., CANT1); thus, these features are not distinctive criteria to predict the molecular basis of DBQD (Furuichi et al., 2011). In addition, Kim et al. (2010) described another milder variant of DBQD with almost normal outwardly appearing hands, but significant radiographic changes, including short metacarpals, elongated phalanges, and remarkably advanced carpal bone age. However, there is no accessory ossification center distal to the second metacarpal, and patients do not have thumb anomalies. Similar changes occur in the feet. These patients also tend to develop precocious osteoarthritis of the hand and spine with age. This phenotype is sometimes referred to as the 'Kim variant' of DBQD (Furuichi et al., 2011). Genetic Heterogeneity of Desbuquois Dysplasia DBQD2 (615777) is caused by mutation in the XYLT1 gene (608124) on chromosome 16p12. Two unrelated patients with immunodeficiency-23 (IMD23; 615816), due to mutation in the PGM3 gene (172100), were reported to have skeletal features reminiscent of DBQD.

Desbuquois dysplasia, which belongs to the multiple dislocation group of disorders, is characterized by dislocations of large joints, severe pre- and postnatal growth retardation, joint laxity, and flat face with prominent eyes. Radiologic features include short long bones with an exaggerated trochanter that gives a 'monkey wrench' appearance to the proximal femur, and advanced carpal and tarsal ossification (summary by Bui et al., 2014). For a discussion of genetic heterogeneity of Desbuquois dysplasia, see DBQD1 (251450).

Rothmund-Thomson syndrome type 3 (RTS3) is characterized by poikiloderma, sparse hair, short stature, and skeletal defects. Patients also exhibit microcephaly, with moderate to severe neurodevelopmental delay and seizures (Averdunk et al., 2023). For a general phenotypic description and discussion of genetic heterogeneity of Rothmund-Thomson syndrome, see RTS2 (268400).

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.

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).

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).

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

CHOPS syndrome is a disorder involving multiple abnormalities that are present from birth (congenital). The name "CHOPS" is an abbreviation for a list of features of the disorder including cognitive impairment, coarse facial features, heart defects, obesity, lung (pulmonary) involvement, short stature, and skeletal abnormalities.\n\nChildren with CHOPS syndrome have intellectual disability and delayed development of skills such as sitting and walking. Characteristic facial features include a round face; thick hair; thick eyebrows that grow together in the middle (synophrys); wide-set, bulging eyes with long eyelashes; a short nose; and down-turned corners of the mouth.\n\nMost affected individuals are born with a heart defect called patent ductus arteriosus (PDA). The ductus arteriosus is a connection between two major arteries, the aorta and the pulmonary artery. This connection is open during fetal development and normally closes shortly after birth. However, the ductus arteriosus remains open, or patent, in babies with PDA. If untreated, this heart defect causes infants to breathe rapidly, feed poorly, and gain weight slowly; in severe cases, it can lead to heart failure. Multiple heart abnormalities have sometimes been found in children with CHOPS syndrome. In addition to PDA, affected individuals may have ventricular septal defect, which is a defect in the muscular wall (septum) that separates the right and left sides of the heart's lower chamber.\n\nPeople with CHOPS syndrome have abnormalities of the throat and airways that cause momentary cessation of breathing while asleep (obstructive sleep apnea). These abnormalities can also cause affected individuals to breathe food or fluids into the lungs accidentally, which can lead to a potentially life-threatening bacterial lung infection (aspiration pneumonia) and chronic lung disease. Affected individuals are shorter than more than 97 percent of their peers and are overweight for their height. They also have skeletal differences including unusually short fingers and toes (brachydactyly) and abnormally-shaped spinal bones (vertebrae).\n\nOther features that can occur in CHOPS syndrome include a small head size (microcephaly); hearing loss; clouding of the lens of the eye (cataract); a single, horseshoe-shaped kidney; and, in affected males, undescended testes (cryptorchidism).

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.

Kosaki overgrowth syndrome (KOGS) is characterized by a facial gestalt involving prominent forehead, proptosis, downslanting palpebral fissures, broad nasal bridge, thin upper lip, and pointed chin. Affected individuals are tall, with an elongated lower segment, and have large hands and feet. Skin is hyperelastic and fragile. Patients exhibit progressive dilatory and vascular changes in basilar/vertebral and coronary arteries starting in the teenage years (Takenouchi et al., 2015; Takenouchi et al., 2021).

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.

Cole-Carpenter syndrome-2 (CLCRP2) is a skeletal dysplasia associated with low bone mass or an osteogenesis imperfecta-like syndrome. It is characterized by bone fragility with craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features such as marked frontal bossing, midface hypoplasia, and micrognathia (summary by Takeyari et al., 2018).

Arboleda-Tham syndrome (ARTHS) is an autosomal dominant disorder with the core features of impaired intellectual development, speech delay, microcephaly, cardiac anomalies, and gastrointestinal complications (summary by Kennedy et al., 2019).

X-linked syndromic intellectual developmental disorder-33 (MRXS33) is an X-linked recessive neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, and characteristic facial features (summary by O'Rawe et al., 2015).

Developmental and epileptic encephalopathy-48 (DEE48) is a severe autosomal recessive neurologic disorder characterized by global developmental delay with intellectual disability and absent speech; poor, if any, motor development; and onset of seizures usually in the first year of life, although later onset has been reported. Affected individuals have poor eye contact and may develop microcephaly and abnormal movements (summary by Assoum et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

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.

Shashi-Pena syndrome is a neurodevelopmental syndrome characterized by delayed psychomotor development, variable intellectual disability, hypotonia, facial dysmorphism, and some unusual features, including enlarged head circumference, glabellar nevus flammeus, and deep palmar creases. Some patients may also have atrial septal defect, episodic hypoglycemia, changes in bone mineral density, and/or seizures (summary by Shashi et al., 2016).

Chitayat syndrome (CHYTS) is a rare condition characterized by respiratory distress presenting at birth, bilateral accessory phalanx resulting in shortened index fingers with ulnar deviation, hallux valgus, and characteristic facial features including prominent eyes, hypertelorism, depressed nasal bridge, full lips, and upturned nose (summary by Balasubramanian et al., 2017).

Any Meier-Gorlin syndrome in which the cause of the disease is a mutation in the CDC45 gene.

Macrocephaly, dysmorphic facies, and psychomotor retardation (MDFPMR) is an autosomal recessive neurodevelopmental disorder characterized by large head and somatic overgrowth apparent at birth followed by global developmental delay. Affected individuals have characteristic dysmorphic facial features and persistently large head, but increased birth weight normalizes with age. Additional neurologic features, including seizures, hypotonia, and gait ataxia, may also occur. Patients show severe intellectual impairment (summary by Ortega-Recalde et al., 2015).

The marfanoid-progeroid-lipodystrophy syndrome (MFLS) is characterized by congenital lipodystrophy, premature birth with an accelerated linear growth disproportionate to weight gain, and progeroid appearance with distinct facial features, including proptosis, downslanting palpebral fissures, and retrognathia. Other characteristic features include arachnodactyly, digital hyperextensibility, myopia, dural ectasia, and normal psychomotor development (Takenouchi et al., 2013). Takenouchi et al. (2013) noted phenotypic overlap with Marfan syndrome (154700) and Shprintzen-Goldberg craniosynostosis syndrome (182212).

Meester-Loeys syndrome (MRLS) is an X-linked disorder characterized by early-onset aortic aneurysm and dissection. Other recurrent findings include hypertelorism, pectus deformity, joint hypermobility, contractures, and mild skeletal dysplasia (Meester et al., 2017).

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).

NMIHBA is a severe autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by global developmental delay apparent from infancy and profoundly impaired intellectual development. Affected individuals have microcephaly with accompanying dysmorphic features, truncal hypotonia, peripheral spasticity, and lack of independent ambulation or speech acquisition. Brain imaging shows variable abnormalities, including cortical atrophy, thin corpus callosum, cerebellar hypoplasia, and delayed myelination (summary by Zollo et al., 2017).

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).

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.

SOST-related sclerosing bone dysplasias include sclerosteosis and van Buchem disease, both disorders of progressive bone overgrowth due to increased bone formation. The major clinical features of sclerosteosis are progressive skeletal overgrowth, most pronounced in the skull and mandible, and variable syndactyly, usually of the second (index) and third (middle) fingers. Affected individuals appear normal at birth except for syndactyly. Facial distortion due to bossing of the forehead and mandibular overgrowth is seen in nearly all individuals and becomes apparent in early childhood with progression into adulthood. Hyperostosis of the skull results in narrowing of the foramina, causing entrapment of the seventh cranial nerve (leading to facial palsy) with other, less common nerve entrapment syndromes including visual loss (2nd cranial nerve), neuralgia or anosmia (5th cranial nerve), and sensory hearing loss (8th cranial nerve). In sclerosteosis, hyperostosis of the calvarium reduces intracranial volume, increasing the risk for potentially lethal elevation of intracranial pressure. Survival of individuals with sclerosteosis into old age is unusual, but not unprecedented. The manifestations of van Buchem disease are generally milder than sclerosteosis and syndactyly is absent; life span appears to be normal.

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.

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.

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.

Trichohepatoenteric syndrome (THES), generally considered to be a neonatal enteropathy, is characterized by intractable diarrhea (seen in almost all affected children), woolly hair (seen in all), intrauterine growth restriction, facial dysmorphism, and short stature. Additional findings include poorly characterized immunodeficiency, recurrent infections, skin abnormalities, and liver disease. Mild intellectual disability (ID) is seen in about 50% of affected individuals. Less common findings include congenital heart defects and platelet anomalies. To date 52 affected individuals have been reported.

Ehlers-Danlos syndrome spondylodysplastic type 1 (EDSSPD1) is characterized by short stature, developmental anomalies of the forearm bones and elbow, and bowing of extremities, in addition to the classic stigmata of Ehlers-Danlos syndrome, including joint laxity, skin hyperextensibility, and poor wound healing. Significant developmental delay is not a consistent feature (Guo et al., 2013). Genetic Heterogeneity of Ehlers-Danlos Syndrome, Spondylodysplastic Type See EDSSPD2 (615349), caused by mutation in the B3GALT6 gene (615291), and EDSSPD3 (612350), caused by mutation in the SLC39A13 gene (608735).

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 with or without polydactyly, see SRTD1 (208500).

Proteasome-associated autoinflammatory syndrome-1 (PRAAS1) is an autosomal recessive disorder characterized by early childhood onset of annular erythematous plaques on the face and extremities with subsequent development of partial lipodystrophy and laboratory evidence of immune dysregulation. More variable features include recurrent fever, severe joint contractures, muscle weakness and atrophy, hepatosplenomegaly, basal ganglia calcifications, and microcytic anemia (summary by Agarwal et al., 2010; Kitamura et al., 2011; Arima et al., 2011). This disorder encompasses Nakajo-Nishimura syndrome (NKJO); joint contractures, muscular atrophy, microcytic anemia, and panniculitis-induced lipodystrophy (JMP syndrome); and chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature syndrome (CANDLE). Among Japanese patients, this disorder is best described as Nakajo-Nishimura syndrome, since both Nakajo (1939) and Nishimura et al. (1950) contributed to the original phenotypic descriptions. Genetic Heterogeneity of Proteasome-Associated Autoinflammatory Syndrome See also PRAAS2 (618048), caused by mutation in the POMP gene (613386) on chromosome 13q12; PRAAS3 (617591), caused by mutation in the PSMB4 gene (602177) on chromosome 1q21; PRAAS4 (619183), caused by mutation in the PSMG2 gene (609702) on chromosome 18p11; PRAAS5 (619175), caused by mutation in the PSMB10 gene (176847) on chromosome 16q22; and PRAAS6 (620796), caused by mutation in the PSMB9 gene (177045) on chromosome 6p21.

ASXL3-related disorder is characterized by developmental delay or intellectual disability, typically in the moderate to severe range, with speech and language delay and/or absent speech. Affected individuals may also display autistic features. There may be issues with feeding. While dysmorphic facial features have been described, they are typically nonspecific. Affected individuals may also have hypotonia that can transition to spasticity resulting in unusual posture with flexion contractions of the elbows, wrists, and fingers. Other findings may include poor postnatal growth, strabismus, seizures, sleep disturbance, and dental anomalies.

Pontocerebellar hypoplasia type 10 is an autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by severely delayed psychomotor development, progressive microcephaly, spasticity, seizures, and brain abnormalities, including brain atrophy and delayed myelination. Some patients have dysmorphic features and an axonal sensorimotor neuropathy (summary by Karaca et al., 2014 and Schaffer et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1 (607596).

Mullegama-Klein-Martinez syndrome (MKMS) is an X-linked recessive disorder with features of microcephaly, microtia, hearing loss, developmental delay, dysmorphic features, congenital heart defect, and digit abnormalities. Females are generally affected more severely than males (Mullegama et al., 2019).

Microcephaly, growth deficiency, seizures, and brain malformations (MIGSB) is a severe autosomal recessive disorder characterized by intrauterine growth retardation, postnatal growth deficiency with severe microcephaly, and poor or absent psychomotor development. Additional features include optic atrophy, early-onset seizures, dysmorphic facial features, and brain malformations, such as partial agenesis of the corpus callosum and simplified gyration (summary by Shaheen et al., 2015).

Houge-Janssens syndrome-3 (HJS3) is characterized by global developmental delay apparent from infancy. The phenotype is highly variable: patients may have hypotonia, behavioral abnormalities, and abnormalities on brain imaging, including enlarged ventricles, thin corpus callosum, and sometimes small brainstem. Many develop seizures, sometimes refractory, and some may have nonspecific dysmorphic features. Intellectual impairment can vary from mild to profound, and some patients may benefit from special education and respond well to speech therapy (summary by Reynhout et al., 2019). For a discussion of genetic heterogeneity of HJS, see HJS1 (616355).

Developmental and epileptic encephalopathy-75 (DEE75) is an autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by onset of severe refractory seizures in the first months of life. Patients often have global developmental delay before the onset of seizures, and thereafter achieve few milestones. EEG usually shows multifocal spikes and hypsarrhythmia, consistent with a clinical diagnosis of West syndrome. They have severely impaired intellectual development with inability to walk, absent speech, and hypotonia with axial hyperreflexia. Brain imaging shows progressive cerebral atrophy, frontal lobe atrophy, white matter abnormalities, and delayed myelination. Since the disorder is due to mitochondrial dysfunction, some patients may develop other organ involvement, including cardiomyopathy or liver and renal dysfunction. Death may occur in childhood (summary by Yin et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Autosomal recessive Robinow syndrome-2 (RRS2) is a skeletal dysplasia characterized by postnatal mesomelic short stature and relative macrocephaly as well as dysmorphic facial features, including frontal bossing, hypertelorism, prominent eyes, wide short nose with anteverted nares, and triangular mouth. Variable other congenital anomalies may be present, including omphalocele, ventral hernia, and cardiac anomalies (White et al., 2018). For a discussion of genetic heterogeneity of autosomal recessive Robinow syndrome, see RRS1 (268310).

Neurodevelopmental disorder with structural brain anomalies and dysmorphic facies (NEDBAF) is a complex syndromic disorder including features of moderate to severe psychomotor delay leading to impaired intellectual development, dysplastic corpus callosum, cortical malformations, hypotonia, dyspraxia, musculoskeletal abnormalities, and feeding difficulties. Seizures occur in about half of patients. Dysmorphic features include wide forehead with frontal bossing and high anterior hairline, prominent eyes with upslanted palpebral fissures, arched eyebrows, long eyelashes, midface hypoplasia, broad nasal bridge, and anteverted nares (summary by Scala et al., 2022).

Developmental and epileptic encephalopathy-80 (DEE80) is an autosomal recessive neurologic disorder characterized by the onset of refractory seizures in the first year of life. Patients have severe global developmental delay and may have additional variable features, including dysmorphic or coarse facial features, distal skeletal abnormalities, and impaired hearing or vision. At the cellular level, the disorder is caused by a defect in the synthesis of glycosylphosphatidylinositol (GPI), and thus affects the expression of GPI-anchored proteins at the cell surface (summary by Murakami et al., 2019). For a discussion of genetic heterogeneity of DEE, see 308350. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).

Rhizomelic limb shortening with dysmorphic features (RLSDF) is characterized by rhizomelic shortening of the extremities, predominantly of the upper limbs, and variable dysmorphic features, including macrocephaly, prominent forehead, hypertelorism, depressed or broad nasal bridge, and micrognathia. Hearing loss has also been observed (Sajan et al., 2019; Pagnamenta et al., 2023).

Spondylometaphyseal dysplasia with corneal dystrophy (SMDCD) is characterized by short stature due to short proximal and distal long bones. Affected individuals also exhibit narrow thorax with pulmonary hypoplasia and respiratory failure, as well as corneal dystrophy. Severe developmental delay has been observed (Ben-Salem et al., 2018).

Mandibuloacral dysplasia with type A lipodystrophy (MADA) is an autosomal recessive disorder characterized by growth retardation, craniofacial anomalies with mandibular hypoplasia, skeletal abnormalities with progressive osteolysis of the distal phalanges and clavicles, and pigmentary skin changes. The lipodystrophy is characterized by a marked acral loss of fatty tissue with normal or increased fatty tissue in the neck and trunk. Some patients may show progeroid features. Metabolic complications can arise due to insulin resistance and diabetes (Young et al., 1971; Simha and Garg, 2002; summary by Garavelli et al., 2009). See also MAD type B (MADB; 608612), which is caused by mutation in the ZMPSTE24 gene (606480).

ROR2-related Robinow syndrome is characterized by distinctive craniofacial features, skeletal abnormalities, and other anomalies. Craniofacial features include macrocephaly, broad prominent forehead, low-set ears, ocular hypertelorism, prominent eyes, midface hypoplasia, short upturned nose with depressed nasal bridge and flared nostrils, large and triangular mouth with exposed incisors and upper gums, gum hypertrophy, misaligned teeth, ankyloglossia, and micrognathia. Skeletal abnormalities include short stature, mesomelic or acromesomelic limb shortening, hemivertebrae with fusion of thoracic vertebrae, and brachydactyly. Other common features include micropenis with or without cryptorchidism in males and reduced clitoral size and hypoplasia of the labia majora in females, renal tract abnormalities, and nail hypoplasia or dystrophy. The disorder is recognizable at birth or in early childhood.

Congenital myopathy-17 (CMYO17) is an autosomal recessive muscle disorder. Affected individuals present at birth with hypotonia and respiratory insufficiency associated with high diaphragmatic dome on imaging. Other features include poor overall growth, pectus excavatum, dysmorphic facies, and renal anomalies in some. The severity of the disorder is highly variable: some patients may have delayed motor development with mildly decreased endurance, whereas others have more severe hypotonia associated with distal arthrogryposis and lung hypoplasia, resulting in early death (summary by Watson et al., 2016 and Lopes et al., 2018). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000).

Mandibuloacral dysplasia progeroid syndrome (MDPS) is an autosomal recessive severe laminopathy-like disorder characterized by growth retardation, bone resorption, arterial calcification, renal glomerulosclerosis, and hypertension (Elouej et al., 2020).

SOFM is characterized by marked short stature, oligodontia, mild facial dysmorphism, and motor delay. Endosteal hyperostosis has also been observed, and patients may exhibit some features of progeria (Terhal et al., 2020; Beauregard-Lacroix et al., 2020).

Marbach-Rustad progeroid syndrome (MARUPS) is characterized by progeroid appearance with little subcutaneous fat and triangular facies, growth retardation with short stature, hypoplastic mandible crowded with unerupted supernumerary teeth, and cerebellar intention tremor. Psychomotor development is normal. Although features are reminiscent of Hutchinson-Gilford progeria syndrome (HGPS; 176670), MARUPS is less severe, with a relatively good prognosis. Two patients have been reported (Marbach et al., 2019).

Otospondylomegaepiphyseal dysplasia (OSMED) is characterized by sensorineural hearing loss, enlarged epiphyses, disproportionate shortness of the limbs, abnormalities in vertebral bodies, and typical facial features (summary by Harel et al., 2005).

Ritscher-Schinzel syndrome-4 (RTSC4) is characterized by a constellation of congenital anomalies, including dysmorphic craniofacial features and structural brain anomalies, such as Dandy-Walker malformation (220200), hindbrain malformations, or agenesis of the corpus callosum, associated with global developmental delay and impaired intellectual development. Congenital cardiac defects have been reported in 1 family (summary by Ritscher et al., 1987 and Jeanne et al., 2021). For a discussion of genetic heterogeneity of Ritscher-Schinzel syndrome, see RTSC1 (220210).

Autosomal recessive cutis laxa type IIE (ARCL2E) is characterized by connective tissue features, including generalized cutis laxa and inguinal hernia, craniofacial dysmorphology, variable mild heart defects, and prominent skeletal features, including craniosynostosis, short stature, brachydactyly, clinodactyly, and syndactyly (Pottie et al., 2021). For a general phenotypic description and discussion of genetic heterogeneity of autosomal recessive cutis laxa, see ARCL1A (219100).

VISS syndrome is a generalized connective tissue disorder characterized by early-onset thoracic aortic aneurysm and other connective tissue findings, such as aneurysm and tortuosity of other arteries, joint hypermobility, skin laxity, and hernias, as well as craniofacial dysmorphic features, structural cardiac defects, skeletal anomalies, and motor developmental delay (Van Gucht et al., 2021). Immune dysregulation has been observed in some patients (Ziegler et al., 2021).

Developmental delay, impaired speech, and behavioral abnormalities (DDISBA) is characterized by global developmental delay apparent from early childhood. Intellectual disability can range from mild to severe. Additional variable features may include dysmorphic facial features, seizures, hypotonia, motor abnormalities such as Tourette syndrome or dystonia, and hearing loss (summary by Cousin et al., 2021).

DEGCAGS syndrome is an autosomal recessive syndromic neurodevelopmental disorder characterized by global developmental delay, coarse and dysmorphic facial features, and poor growth and feeding apparent from infancy. Affected individuals have variable systemic manifestations often with significant structural defects of the cardiovascular, genitourinary, gastrointestinal, and/or skeletal systems. Additional features may include sensorineural hearing loss, hypotonia, anemia or pancytopenia, and immunodeficiency with recurrent infections. Death in childhood may occur (summary by Bertoli-Avella et al., 2021).

Craniotubular dysplasia, Ikegawa type (CTDI) is characterized by childhood-onset short stature in association with macrocephaly, dolichocephaly, or prominent forehead. Radiography shows hyperostosis of the calvaria and skull base, with metadiaphyseal undermodeling of the long tubular bones and mild shortening and diaphyseal broadening of the short tubular bones. Affected individuals experience progressive vision loss in the first decade of life due to optic nerve compression, and deafness may develop in the second decade of life (Guo et al., 2021).

Teebi hypertelorism syndrome-2 (TBHS2) is characterized primarily by hypertelorism, prominent forehead, thick and broad eyebrows, and short nose with depressed nasal root and broad nasal tip. Other features include thin upper lip, small chin with horizontal crease, and high or cleft palate. Developmental delay and/or impaired intellectual development have been observed in some patients (Li et al., 2021). For a general phenotypic description and a discussion of genetic heterogeneity of Teebi hypertelorism syndrome, see TBHS1 (145420).

Restrictive dermopathy is a rare genodermatosis characterized mainly by intrauterine growth retardation, tight and rigid skin with erosions, prominent superficial vasculature and epidermal hyperkeratosis, facial dysmorphism (small mouth, small pinched nose and micrognathia), sparse/absent eyelashes and eyebrows, mineralization defects of the skull, thin dysplastic clavicles, pulmonary hypoplasia, multiple joint contractures, and an early neonatal lethal course. Liveborn children usually die within the first week of life (summary by Navarro et al., 2004). For a discussion of genetic heterogeneity of restrictive dermopathy, see RSDM1 (275210).

Severe congenital liver disease (SCOLIV) is an autosomal recessive disorder characterized by the onset of progressive hepatic dysfunction usually in the first years of life. Affected individuals show feeding difficulties with failure to thrive and features such as jaundice, hepatomegaly, and abdominal distension. Laboratory workup is consistent with hepatic insufficiency and may also show coagulation defects, anemia, or metabolic disturbances. Cirrhosis and hypernodularity are commonly observed on liver biopsy. Many patients die of liver failure in early childhood (Moreno Traspas et al., 2022).

Neurodevelopmental disorder with hypotonia, language delay, and skeletal defects with or without seizures (NEDHLSS) is characterized by global developmental delay apparent from infancy. Affected individuals show severe hypotonia with delayed walking or inability to walk, poor or absent speech, and impaired intellectual development with behavioral abnormalities. Most patients have early-onset seizures, mild skeletal defects that are usually distal, and nonspecific dysmorphic features. More severely affected individuals have additional congenital abnormalities; however, cardiac involvement is rare (summary by Rodan et al., 2021).

Neurodevelopmental disorder with seizures, spasticity, and partial or complete agenesis of the corpus callosum (NEDSSCC) is an autosomal recessive disorder characterized by axial hypotonia and global developmental delay apparent from the first days or months of life. Affected individuals often have feeding difficulties and develop early-onset seizures that tend to be well-controlled. Other features include peripheral spasticity with hyperreflexia, variable dysmorphic features, impaired intellectual development, behavioral abnormalities, and hypoplasia or absence of the corpus callosum on brain imaging (Faqeih et al., 2023).

Classic congenital myopathy-22A (CMYO22A) is an autosomal recessive muscle disorder characterized by onset of muscle weakness in utero or soon after birth. Early features may include fetal hypokinesia, breech presentation, and polyhydramnios. Affected individuals are born with severe hypotonia and require respiratory and feeding assistance. Those who survive the neonatal period show a 'classic' phenotype of congenital myopathy with delayed motor development, difficulty walking, proximal muscle weakness of the upper and lower limbs, facial and neck muscle weakness, easy fatigability, and mild limb contractures or foot deformities. Some have persistent respiratory insufficiency; dysmorphic facial features may be present (Zaharieva et al., 2016). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000).

Severe fetal congenital myopathy-22B (CMYO22B) is an autosomal recessive muscle disorder characterized by in utero onset of severe muscle weakness manifest as fetal akinesia. The pregnancies are often complicated by polyhydramnios, and affected individuals develop fetal hydrops with pulmonary hypoplasia, severe joint contractures, and generalized muscle hypoplasia. Those who are born have respiratory failure resulting in death. Dysmorphic facial features may be present. The features in these patients overlap with fetal akinesia deformation sequence (FADS; see 208150) and lethal congenital contractures syndrome (LCCS; see 253310) (Zaharieva et al., 2016). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000).

Craniometadiaphyseal osteosclerosis with hip dysplasia (CMDOH) is characterized by macrocephaly, cranial hyperostosis, and vertebral endplate sclerosis. Other frequent findings include hip dysplasia, heart malformations, variable developmental delay, and hematologic anomalies including anemia and pancytopenia. Bone biopsy shows evidence of increased osteoblast and reduced osteoclast function at the growth plate resorption zone, resulting in coarse trabeculae (Terhal et al., 2023). For syndromes with overlapping features, see osteopetrosis, autosomal recessive (OPTB1; 259700) and dominant (OPTA1; 607634), and osteopathia with cranial sclerosis (OSCS; 300373).

The Guo-Campeau type of spondyloepimetaphyseal dysplasia (SEMDGC) is characterized by severe bone dysplasia resulting in significant short stature with variable anomalies of the spine, pelvis, hips, and extremities, including short, rudimentary, or absent digits. Patients also exhibit variable facial dysmorphisms (Guo et al., 2023). Biallelic null mutations in the ERI1 gene have been reported to cause a less severe disorder, Hoxha-Alia syndrome, involving digital anomalies and mild intellectual disability (HXAL; 620662).

Jeffries-Lakhani neurodevelopmental syndrome (JELANS) is an autosomal recessive disorder characterized by hypotonia, early-onset seizures, and global developmental delay apparent from infancy. Affected individuals have motor delay, speech delay, and impaired intellectual development, and about half of patients are nonambulatory and/or nonverbal. Some patients have cardiac arrhythmia, but congenital cardiac septal defects are only rarely observed. Additional features may include feeding difficulties, recurrent infections, ocular defects, and nonspecific dysmorphic features. Premature death due to cardiac arrhythmia or epilepsy may occur (Jeffries et al., 2024).

Autosomal recessive idiopathic basal ganglia calcification-9 (IBGC9) is characterized by a combination of features including ataxia, parkinsonism, headache, and psychiatric and cognitive deficits, with high intrafamilial phenotypic variability and age at onset (Chelban et al., 2024). For a phenotypic description and a discussion of genetic heterogeneity of IBGC, see IBGC1 (213600).

El Hayek-Chahrour neurodevelopmental disorder (NEDEHC) is characterized by absent speech, impaired intellectual development, and autism (El Hayek et al., 2020).