Choroideremia (CHM) is characterized by progressive chorioretinal degeneration in affected males and milder signs in heterozygous (carrier) females. Typically, symptoms in affected males evolve from night blindness to peripheral visual field loss, with central vision preserved until late in life. Although carrier females are generally asymptomatic, signs of chorioretinal degeneration can be reliably observed with fundus autofluorescence imaging, and – after age 25 years – with careful fundus examination.

Gyrate atrophy of the choroid and retina (GACR) due to deficiency of ornithine aminotransferase is clinically characterized by a triad of progressive chorioretinal degeneration, early cataract formation, and type II muscle fiber atrophy. Characteristic chorioretinal atrophy with progressive constriction of the visual fields leads to blindness at the latest during the sixth decade of life. Patients generally have normal intelligence (summary by Peltola et al., 2002). See 238970 for another hyperornithinemia syndrome.

PNPLA6 disorders span a phenotypic continuum characterized by variable combinations of cerebellar ataxia; upper motor neuron involvement manifesting as spasticity and/or brisk reflexes; chorioretinal dystrophy associated with variable degrees of reduced visual function; and hypogonadotropic hypogonadism (delayed puberty and lack of secondary sex characteristics). The hypogonadotropic hypogonadism occurs either in isolation or as part of anterior hypopituitarism (growth hormone, thyroid hormone, or gonadotropin deficiencies). Common but less frequent features are peripheral neuropathy (usually of axonal type manifesting as reduced distal reflexes, diminished vibratory sensation, and/or distal muscle wasting); hair anomalies (long eyelashes, bushy eyebrows, or scalp alopecia); short stature; and impaired cognitive functioning (learning disabilities in children; deficits in attention, visuospatial abilities, and recall in adults). Some of these features can occur in distinct clusters on the phenotypic continuum: Boucher-Neuhäuser syndrome (cerebellar ataxia, chorioretinal dystrophy, and hypogonadotropic hypogonadism); Gordon Holmes syndrome (cerebellar ataxia, hypogonadotropic hypogonadism, and – to a variable degree – brisk reflexes); Oliver-McFarlane syndrome (trichomegaly, chorioretinal dystrophy, short stature, intellectual disability, and hypopituitarism); Laurence-Moon syndrome; and spastic paraplegia type 39 (SPG39) (upper motor neuron involvement, peripheral neuropathy, and sometimes reduced cognitive functioning and/or cerebellar ataxia).

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a disorder of the urea cycle and ornithine degradation pathway. Clinical manifestations and age of onset vary among individuals even in the same family. Neonatal onset (~8% of affected individuals). Manifestations of hyperammonemia usually begin 24-48 hours after feeding begins and can include lethargy, somnolence, refusal to feed, vomiting, tachypnea with respiratory alkalosis, and/or seizures. Infantile, childhood, and adult onset (~92%). Affected individuals may present with: Chronic neurocognitive deficits (including developmental delay, ataxia, spasticity, learning disabilities, cognitive deficits, and/or unexplained seizures); Acute encephalopathy secondary to hyperammonemic crisis precipitated by a variety of factors; and Chronic liver dysfunction (unexplained elevation of liver transaminases with or without mild coagulopathy, with or without mild hyperammonemia and protein intolerance). Neurologic findings and cognitive abilities can continue to deteriorate despite early metabolic control that prevents hyperammonemia.

Progressive bifocal chorioretinal atrophy (PBCRA) is a rare, autosomal dominant congenital chorioretinal dystrophy. The disorder is characterized by progressive macular and nasal retinal atrophic lesions, nystagmus, myopia, and poor vision. Invariably, there are 2 distinct foci of atrophy, a temporal focus that is present at birth and a nasal focus that appears early in life. Retinal detachment is an additional complication of the disease (Douglas et al., 1968; Kelsell et al., 1995).

Any retinitis pigmentosa in which the cause of the disease is a mutation in the NRL gene.

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).

VCAN-related vitreoretinopathy, which includes Wagner syndrome and erosive vitreoretinopathy (ERVR), is characterized by "optically empty vitreous" on slit-lamp examination and avascular vitreous strands and veils, mild or occasionally moderate to severe myopia, presenile cataract, night blindness of variable degree associated with progressive chorioretinal atrophy, retinal traction and retinal detachment in the advanced stages of disease, and reduced visual acuity. Optic nerve inversion as well as uveitis has also been described. Systemic abnormalities are not observed. The first signs usually become apparent during early adolescence, but onset can be as early as age two years.

A retinitis pigmentosa that has material basis in mutation in the PRPH2 gene on chromosome 6p21.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the FSCN2 gene.

PNPLA6 disorders span a phenotypic continuum characterized by variable combinations of cerebellar ataxia; upper motor neuron involvement manifesting as spasticity and/or brisk reflexes; chorioretinal dystrophy associated with variable degrees of reduced visual function; and hypogonadotropic hypogonadism (delayed puberty and lack of secondary sex characteristics). The hypogonadotropic hypogonadism occurs either in isolation or as part of anterior hypopituitarism (growth hormone, thyroid hormone, or gonadotropin deficiencies). Common but less frequent features are peripheral neuropathy (usually of axonal type manifesting as reduced distal reflexes, diminished vibratory sensation, and/or distal muscle wasting); hair anomalies (long eyelashes, bushy eyebrows, or scalp alopecia); short stature; and impaired cognitive functioning (learning disabilities in children; deficits in attention, visuospatial abilities, and recall in adults). Some of these features can occur in distinct clusters on the phenotypic continuum: Boucher-Neuhäuser syndrome (cerebellar ataxia, chorioretinal dystrophy, and hypogonadotropic hypogonadism); Gordon Holmes syndrome (cerebellar ataxia, hypogonadotropic hypogonadism, and – to a variable degree – brisk reflexes); Oliver-McFarlane syndrome (trichomegaly, chorioretinal dystrophy, short stature, intellectual disability, and hypopituitarism); Laurence-Moon syndrome; and spastic paraplegia type 39 (SPG39) (upper motor neuron involvement, peripheral neuropathy, and sometimes reduced cognitive functioning and/or cerebellar ataxia).

Sorsby fundus dystrophy (SFD) is an autosomal dominant retinal dystrophy characterized by the loss of central vision as a result of macular disease by the fourth to fifth decade and peripheral visual loss in late life (summary by Wijesuriya et al., 1996).

PAX2-related disorder is an autosomal dominant disorder associated with renal and eye abnormalities. The disorder was originally referred to as renal coloboma syndrome and characterized by renal hypodysplasia and abnormalities of the optic nerve; with improved access to molecular testing, a wider range of phenotypes has been recognized in association with pathogenic variants in PAX2. Abnormal renal structure or function is noted in 92% of affected individuals and ophthalmologic abnormalities in 77% of affected individuals. Renal abnormalities can be clinically silent in rare individuals. In most individuals, clinically significant renal insufficiency / renal failure is reported. End-stage renal disease requiring renal transplant is not uncommon. Uric acid nephrolithiasis has been reported. Ophthalmologic abnormalities are typically described as optic nerve coloboma or dysplasia. Iris colobomas have not been reported in any individual with PAX2–related disorder. Ophthalmologic abnormalities may significantly impair vision in some individuals, while others have subtle changes only noted after detailed ophthalmologic examination. Additional clinical findings include high-frequency sensorineural hearing loss, soft skin, and ligamentous laxity. PAX2 pathogenic variants have been identified in multiple sporadic and familial cases of nonsyndromic renal disease including renal hypodysplasia and focal segmental glomerulosclerosis.

A syndromic disorder with the association between Dandy-Walker malformation and postaxial polydactyly as a major feature. The Dandy-Walker malformation has a variable expression and characteristics of a posterior fossa cyst communicating with the fourth ventricle, the partial or complete absence of the cerebellar vermis, and facultative hydrocephalus. Postaxial polydactyly includes tetramelic postaxial polydactyly of hands and feet with possible enlargement of the fifth metacarpal and metatarsal bones, as well as bifid fifth metacarpals.

PNPLA6 disorders span a phenotypic continuum characterized by variable combinations of cerebellar ataxia; upper motor neuron involvement manifesting as spasticity and/or brisk reflexes; chorioretinal dystrophy associated with variable degrees of reduced visual function; and hypogonadotropic hypogonadism (delayed puberty and lack of secondary sex characteristics). The hypogonadotropic hypogonadism occurs either in isolation or as part of anterior hypopituitarism (growth hormone, thyroid hormone, or gonadotropin deficiencies). Common but less frequent features are peripheral neuropathy (usually of axonal type manifesting as reduced distal reflexes, diminished vibratory sensation, and/or distal muscle wasting); hair anomalies (long eyelashes, bushy eyebrows, or scalp alopecia); short stature; and impaired cognitive functioning (learning disabilities in children; deficits in attention, visuospatial abilities, and recall in adults). Some of these features can occur in distinct clusters on the phenotypic continuum: Boucher-Neuhäuser syndrome (cerebellar ataxia, chorioretinal dystrophy, and hypogonadotropic hypogonadism); Gordon Holmes syndrome (cerebellar ataxia, hypogonadotropic hypogonadism, and – to a variable degree – brisk reflexes); Oliver-McFarlane syndrome (trichomegaly, chorioretinal dystrophy, short stature, intellectual disability, and hypopituitarism); Laurence-Moon syndrome; and spastic paraplegia type 39 (SPG39) (upper motor neuron involvement, peripheral neuropathy, and sometimes reduced cognitive functioning and/or cerebellar ataxia).

Bietti crystalline dystrophy (BCD) is a chorioretinal degeneration characterized by the presence of yellow-white crystals and/or complex lipid deposits in the retina and (to a variable degree) the cornea. Progressive atrophy and degeneration of the retinal pigment epithelium (RPE) / choroid lead to symptoms similar to those of other forms of retinal degeneration that fall under the category of retinitis pigmentosa and allied disorders, namely: reduced visual acuity, poor night vision, abnormal retinal electrophysiology, visual field loss, and often impaired color vision. Marked asymmetry between eyes is not uncommon. Onset is typically during the second to third decade of life, but ranges from the early teenage years to beyond the third decade. With time, loss of peripheral visual field, central acuity, or both result in legal blindness in most if not all affected individuals.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the EYS gene.

There are more than 30 types of cone-rod dystrophy, which are distinguished by their genetic cause and their pattern of inheritance: autosomal recessive, autosomal dominant, and X-linked. Additionally, cone-rod dystrophy can occur alone without any other signs and symptoms or it can occur as part of a syndrome that affects multiple parts of the body.\n\nThe first signs and symptoms of cone-rod dystrophy, which often occur in childhood, are usually decreased sharpness of vision (visual acuity) and increased sensitivity to light (photophobia). These features are typically followed by impaired color vision (dyschromatopsia), blind spots (scotomas) in the center of the visual field, and partial side (peripheral) vision loss. Over time, affected individuals develop night blindness and a worsening of their peripheral vision, which can limit independent mobility. Decreasing visual acuity makes reading increasingly difficult and most affected individuals are legally blind by mid-adulthood. As the condition progresses, individuals may develop involuntary eye movements (nystagmus).\n\nCone-rod dystrophy is a group of related eye disorders that causes vision loss, which becomes more severe over time. These disorders affect the retina, which is the layer of light-sensitive tissue at the back of the eye. In people with cone-rod dystrophy, vision loss occurs as the light-sensing cells of the retina gradually deteriorate.

Alagille syndrome (ALGS) is a multisystem disorder with a wide spectrum of clinical variability; this variability is seen even among individuals from the same family. The major clinical manifestations of ALGS are bile duct paucity on liver biopsy, cholestasis, congenital cardiac defects (primarily involving the pulmonary arteries), butterfly vertebrae, ophthalmologic abnormalities (most commonly posterior embryotoxon), and characteristic facial features. Renal abnormalities, growth failure, developmental delays, splenomegaly, and vascular abnormalities may also occur.

Oculoauricular syndrome (OCACS) is characterized by complex ocular anomalies, including congenital cataract, anterior segment dysgenesis, iris coloboma, and early-onset retinal dystrophy, and dysplastic ears with abnormal external ear cartilage (summary by Gillespie et al., 2015).

Central areolar choroidal dystrophy-2 (CACD2) is a hereditary retinal disorder that principally affects the macula, often resulting in a well-defined area of atrophy of the retinal pigment epithelium (RPE) and choriocapillaris in the center of the macula. Dysfunction of macular photoreceptors usually leads to a decrease in visual acuity, generally occurring between the ages of 30 and 60 years (summary by Boon et al., 2009). For a discussion of genetic heterogeneity of central areolar choroidal dystrophy, see CACD1 (215500).

Retinitis pigmentosa-47 (RP47) is characterized by relatively late-onset visual decline, although most patients experience night blindness in childhood. A characteristic golden sheen, considered to be pathognomonic for Oguchi disease (258100), may be observed in the periphery on ultra-widefield fundus images (Nishiguchi et al., 2019). For a phenotypic description and a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000.

Leber congenital amaurosis comprises a group of early-onset childhood retinal dystrophies characterized by vision loss, nystagmus, and severe retinal dysfunction. Patients usually present at birth with profound vision loss and pendular nystagmus. Electroretinogram (ERG) responses are usually nonrecordable. Other clinical findings may include high hypermetropia, photodysphoria, oculodigital sign, keratoconus, cataracts, and a variable appearance to the fundus (summary by Chung and Traboulsi, 2009). For a general description and a discussion of genetic heterogeneity of LCA, see 204000.

Cone-rod dystrophy (CORD) characteristically leads to early impairment of vision. An initial loss of color vision and of visual acuity is followed by nyctalopia (night blindness) and loss of peripheral visual fields. In extreme cases, these progressive symptoms are accompanied by widespread, advancing retinal pigmentation and chorioretinal atrophy of the central and peripheral retina (Moore, 1992). In many families, perhaps a majority, central and peripheral chorioretinal atrophy is not found (Tzekov, 1998). Genetic Heterogeneity of Autosomal Cone-Rod Dystrophy There are several other autosomal forms of CORD for which the molecular basis is known. CORD3 (604116) is caused by mutation in the ABCA4 gene (601691) on chromosome 1p22. CORD5 (600977) is caused by mutation in the PITPNM3 gene (608921) on chromosome 17p13. CORD6 (601777) is caused by mutation in the GUCY2D gene (600179) on chromosome 17p13.1. CORD9 (612775) is caused by mutation in the ADAM9 gene (602713) on chromosome 8p11. CORD10 (610283) is caused by mutation in the SEMA4A gene (607292) on chromosome 1q22. CORD11 (610381) is caused by mutation in the RAXL1 gene (610362) on chromosome 19p13. CORD12 (612657) is caused by mutation in the PROM1 gene (604365) on chromosome 4p15. CORD13 (608194) is caused by mutation in the RPGRIP1 gene (605446) on chromosome 14q11. CORD14 (see 602093) is caused by mutation in the GUCA1A gene (600364) on chromosome 6p21. CORD15 (613660) is caused by mutation in the CDHR1 gene (609502) on chromosome 10q23. CORD16 (614500) is caused by mutation in the C8ORF37 gene (614477) on chromosome 8q22. CORD18 (615374) is caused by mutation in the RAB28 gene (612994) on chromosome 4p15. CORD19 (615860) is caused by mutation in the TTLL5 gene (612268) on chromosome 14q24. CORD20 (615973) is caused by mutation in the POC1B gene (614784) on chromosome 12q21. CORD21 (616502) is caused by mutation in the DRAM2 gene (613360) on chromosome 1p13. CORD22 (619531) is caused by mutation in the TLCD3B gene (615175) on chromosome 16p11. CORD23 (see 613428) is caused by mutation in the C2ORF71 gene (PCARE; 613425) on chromosome 2p23. CORD24 (620342) is caused by mutation in the UNC119 gene (604011) on chromosome 17q11. A diagnosis of CORD was made in an individual with a mutation in the AIPL1 gene (604392.0004) on chromosome 17p13.1, as well as in an individual with a mutation in the UNC119 gene (604011.0001) on chromosome 17q11.2. Other mapped loci for autosomal CORD include CORD1 (600624) on chromosome 18q21.1-q21.3; CORD7 (603649) on chromosome 6q14; CORD8 (605549) on chromosome 1q12-q24; and CORD17 (615163) on chromosome 10q26. For a discussion of X-linked forms of cone-rod dystrophy, see CORDX1 (304020).

An X-linked retinal dystrophy characterized by choroideremia, causing in affected males progressive nyctalopia and eventual central blindness. Obesity, moderate intellectual disability and congenital mixed (sensorineural and conductive) deafness are also observed. Female carriers show typical retinal changes indicative of the choroideremia carrier state.

Familial exudative vitreoretinopathy is a hereditary disorder that can cause vision loss that worsens over time. This condition affects the retina, the specialized light-sensitive tissue that lines the back of the eye. In people with this disorder, blood vessels do not fully develop at the outer edges (periphery) of the retina, which reduces the blood supply to this tissue. This prolonged reduction in blood supply (chronic ischemia) causes continued damage to the retina and can lead to worsening of the condition. \n\nThe signs and symptoms of familial exudative vitreoretinopathy vary widely, even within the same family. In many affected individuals, the retinal abnormalities never cause any vision problems. Other people with this condition develop abnormal vessels that leak. This  causes chronic inflammation which, over time, can lead to fluid under the retina (exudate). A reduction in the retina's blood supply causes the retina to fold, tear, or separate from the back of the eye (retinal detachment). The resulting retinal damage can lead to vision loss and blindness. Other eye abnormalities are also possible, including eyes that do not look in the same direction (strabismus) and a visible whiteness (leukocoria) in the normally black pupil.\n\nSome people with familial exudative vitreoretinopathy also have a condition known as osteoporosis-pseudoglioma syndrome, which is characterized by reduced bone density. People with this condition have weakened bones and an increased risk of fractures.

Knobloch syndrome-1 (KNO1) is an autosomal recessive developmental disorder primarily characterized by typical eye abnormalities, including high myopia, cataracts, dislocated lens, vitreoretinal degeneration, and retinal detachment, with occipital skull defects, which can range from occipital encephalocele to occult cutis aplasia (summary by Aldahmesh et al., 2011). Genetic Heterogeneity of Knobloch Syndrome KNO2 (618458) is caused by mutation in the PAK2 gene (605022) on chromosome 3q29.

Any central areolar choroidal dystrophy in which the cause of the disease is a mutation in the GUCY2D gene.

CLCN2-related leukoencephalopathy is characterized by nonspecific neurologic findings, mild visual impairment from chorioretinopathy or optic atrophy, male infertility, and characteristic findings on brain MRI. Neurologic findings include mild ataxia (action tremor and gait instability following initially normal motor development; occasionally, mild spasticity), cognitive impairment in some (typically mild, rarely severe), psychiatric symptoms in some (depression and schizophrenia-like symptoms), headaches in some (usually intermittent, severe, and diffuse) and auditory symptoms in some (hearing loss, tinnitus, vertigo). Affected individuals remain ambulatory, do not require support for walking, and rarely become blind. To date CLCN2-related leukoencephalopathy has been reported or identified in 31 individuals from 30 families. It is not yet known if the findings occurring in a few individuals (i.e., epilepsy and paroxysmal kinesigenic dyskinesia) are part of the phenotypic spectrum or unrelated findings.

Retinitis pigmentosa-87 with choroidal involvement (RP87) is characterized by a slowly progressive visual disturbance, including night blindness and reduced central and peripheral vision, accompanied by extensive choroid/retinal atrophy that mimics certain aspects of choroideremia. Disease severity and age of onset are variable, and some carriers are unaffected (Hull et al., 2016; Li et al., 2019). For a discussion of genetic heterogeneity of RP, see 268000.

Aicardi-Goutieres syndrome-9 (AGS9) is a type I interferonopathy characterized by severe developmental delay and progressive neurologic deterioration. Patients present in infancy with irritability and spasticity. Brain imaging shows diffusely abnormal white matter, cerebral atrophy, and intracranial calcification. Premature death has been associated with renal and/or hepatic failure (Uggenti et al., 2020). For a general phenotypic description and discussion of genetic heterogeneity of Aicardi-Goutieres syndrome, see AGS1 (225750).