Sjogren-Larsson syndrome (SLS) is an autosomal recessive, early childhood-onset disorder characterized by ichthyosis, impaired intellectual development, spastic paraparesis, macular dystrophy, and leukoencephalopathy. It is caused by deficiency of fatty aldehyde dehydrogenase (summary by Lossos et al., 2006).

The neuronal ceroid lipofuscinoses (NCL; CLN) are a clinically and genetically heterogeneous group of neurodegenerative disorders characterized by the intracellular accumulation of autofluorescent lipopigment storage material in different patterns ultrastructurally. The clinical course includes progressive dementia, seizures, and progressive visual failure (Mole et al., 2005). The hallmark of CLN3 is the ultrastructural pattern of lipopigment with a 'fingerprint' profile, which can have 3 different appearances: pure within a lysosomal residual body; in conjunction with curvilinear or rectilinear profiles; and as a small component within large membrane-bound lysosomal vacuoles. The combination of fingerprint profiles within lysosomal vacuoles is a regular feature of blood lymphocytes from patients with CLN3 (Mole et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of CLN, see CLN1 (256730).

Spinocerebellar ataxia type 7 (SCA7) comprises a phenotypic spectrum ranging from adolescent- or adult-onset progressive cerebellar ataxia and cone-rod retinal dystrophy to infantile or early-childhood onset with multiorgan failure, an accelerated course, and early death. Anticipation in this nucleotide repeat disorder may be so dramatic that within a family a child with infantile or early-childhood onset may be diagnosed with what is thought to be an unrelated neurodegenerative disorder years before a parent or grandparent with a CAG repeat expansion becomes symptomatic. In adolescent-onset SCA7, the initial manifestation is typically impaired vision, followed by cerebellar ataxia. In those with adult onset, progressive cerebellar ataxia usually precedes the onset of visual manifestations. While the rate of progression varies in these two age groups, the eventual result for almost all affected individuals is loss of vision, severe dysarthria and dysphagia, and a bedridden state with loss of motor control.

Pseudoxanthoma elasticum (PXE) is a systemic disorder that affects the elastic tissue of the skin, the eye, and vascular system. Individuals most commonly present with angioid streaks of the retina found on routine eye examination or associated with retinal hemorrhage and/or characteristic papules in the skin. The most frequent cause of morbidity and disability in PXE is reduced vision due to complications of subretinal neovascularizations and macular atrophy. Other manifestations include premature gastrointestinal angina and/or bleeding, intermittent claudication of arm and leg muscles, stroke, renovascular hypertension, and cardiovascular complications (angina/myocardial infarction). Most affected individuals live a normal life span.

Hypotrichosis with juvenile macular degeneration (HJMD) is a very rare syndrome characterized by sparse and short hair from birth followed by progressive macular degeneration leading to blindness.

Cone-rod dystrophy-5 (CORD5) is characterized by reduced visual acuity, photophobia, and defective color vision. Most patients experience onset of symptoms in early childhood, with progression to legal blindness by early adulthood, although some patients exhibit a milder phenotype, with onset in the fourth or fifth decade of life (Kohn et al., 2007; Reinis et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of cone-rod dystrophy, see 120970.

The 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\nThere 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\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.

Age-related macular degeneration-3 (ARMD3) is characterized by numerous small round yellow lesions visible at the temporal edge of the macula. Larger, less distinct yellow areas near the center of the macula are also observed, which represent areas of pigment epithelial detachment (Stone et al., 2004). For a phenotypic description and a discussion of genetic heterogeneity of age-related macular degeneration, see 603075.

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of retinal dystrophies characterized by a progressive degeneration of photoreceptors, eventually resulting in severe visual impairment. For a discussion of genetic heterogeneity of RP, see 268000.

Caused by mutation in the gene encoding retinaldehyde-binding protein-1. A high frequency of a distinctive form of retinal dystrophy was found to occur in northern Sweden. Typical manifestations are night blindness from early childhood and in young adults retinitis punctata albescens was observed followed by macular degeneration.

Cone-rod dystrophy-10 (CORD10) is characterized by progressive loss of visual acuity and color vision, followed by night blindness and loss of peripheral vision. Patients may experience photophobia and epiphora in bright light (Abid et al., 2006). Mutation in SEMA4A can also cause a form of retinitis pigmentosa (RP35; 610282). For a general phenotypic description and a discussion of genetic heterogeneity of cone-rod dystrophy, see 120970.

Spastic paraplegia 15 (SPG15), typically an early-onset complex hereditary spastic paraplegia, is characterized by progressive spasticity that begins in the lower extremities and is associated with several manifestations resulting from central and peripheral nervous system dysfunction. While onset of spasticity is typically in mid- to late childhood or adolescence (i.e., between ages 5 and 18 years), other manifestations, such as developmental delay or learning disability, may be present earlier, often preceding motor involvement. Individuals with adult onset have also been reported.

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

The neuronal ceroid lipofuscinoses (NCL; CLN) are a clinically and genetically heterogeneous group of neurodegenerative disorders characterized by the intracellular accumulation of autofluorescent lipopigment storage material in different patterns ultrastructurally. The lipopigment pattern seen most often in CLN1 is referred to as granular osmiophilic deposits (GROD). The patterns most often observed in CLN2 and CLN3 are 'curvilinear' and 'fingerprint' profiles, respectively. CLN4, CLN5, CLN6, CLN7, and CLN8 show mixed combinations of granular, curvilinear, fingerprint, and rectilinear profiles. The clinical course includes progressive dementia, seizures, and progressive visual failure (Mole et al., 2005). Zeman and Dyken (1969) referred to these conditions as the 'neuronal ceroid lipofuscinoses.' Goebel (1995) provided a comprehensive review of the NCLs and noted that they are possibly the most common group of neurodegenerative diseases in children. Mole et al. (2005) provided a detailed clinical and genetic review of the neuronal ceroid lipofuscinoses. Genetic Heterogeneity of Neuronal Ceroid Lipofuscinosis See also CLN2 (204500), caused by mutation in the TPP1 gene (607998) on chromosome 11p15; CLN3 (204200), caused by mutation in the CLN3 gene (607042) on 16p12; CLN4 (162350), caused by mutation in the DNAJC5 gene (611203) on 20q13; CLN5 (256731), caused by mutation in the CLN5 gene (608102) on 13q22; CLN6A (601780) and CLN6B (204300), both caused by mutation in the CLN6 gene (606725) on 15q21; CLN7 (610951), caused by mutation in the MFSD8 gene (611124) on 4q28; CLN8 (600143) and the Northern epilepsy variant of CLN8 (610003), both caused by mutation in the CLN8 gene (607837) on 8p23; CLN10 (610127), caused by mutation in the CTSD gene (116840) on 11p15; CLN11 (614706), caused by mutation in the GRN gene (138945) on 17q21; CLN13 (615362), caused by mutation in the CTSF gene (603539) on 11q13; and CLN14 (611726), caused by mutation in the KCTD7 gene (611725) on 7q11. CLN9 (609055) has not been molecularly characterized. A disorder that was formerly designated neuronal ceroid lipofuscinosis-12 (CLN12) is now considered to be a variable form of Kufor-Rakeb syndrome (KRS; 606693).

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.

Age-related macular degeneration-4 (ARMD) is a disorder of the eye characterized by the formation of drusen on the retina, often as cuticular drusen which appear in a 'starry sky' distribution on fluorescein angiography. The disorder results in a progressive loss of central vision (summary by Hageman et al., 2005, Grassi et al., 2007).

A cone-rod dystrophy that has material basis in variation in the chromosome region 1q12-q24.

Stargardt macular degeneration is a genetic eye disorder that causes progressive vision loss. This disorder affects the retina, the specialized light-sensitive tissue that lines the back of the eye. Specifically, Stargardt macular degeneration affects a small area near the center of the retina called the macula. The macula is responsible for the type of vision needed for detailed tasks such as reading, driving, and recognizing faces. In most people with Stargardt macular degeneration, a fatty yellow pigment called lipofuscin builds up in cells underlying the macula. Over time, the abnormal accumulation of this substance can damage cells that are critical for clear vision. People with Stargardt macular degeneration have problems with night vision that can make it difficult to navigate in low light. Some affected individuals also have impaired color vision. The signs and symptoms of Stargardt macular degeneration typically appear in late childhood to early adulthood and worsen over time.

Age-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.\n\nAge-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.\n\nResearchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.\n\nIn 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.

Spastic paraplegia 11 (SPG11) is characterized by progressive spasticity and weakness of the lower limbs frequently associated with the following: mild intellectual disability with learning difficulties in childhood and/or progressive cognitive decline; peripheral neuropathy; pseudobulbar involvement; and increased reflexes in the upper limbs. Less frequent findings include: cerebellar signs (ataxia, nystagmus, saccadic pursuit); retinal degeneration; pes cavus; scoliosis; and parkinsonism with characteristic brain MRI features that include thinning of the corpus callosum. Onset occurs mainly during infancy or adolescence (range: age 1-31 years) and in rare cases as late as age 60 years. Most affected individuals become wheelchair bound one or two decades after disease onset.

Stargardt disease (STGD) is the most common hereditary macular dystrophy and is characterized by decreased central vision, atrophy of the macula and underlying retinal pigment epithelium, and frequent presence of prominent flecks in the posterior pole of the retina. STGD is most commonly inherited as an autosomal recessive trait (see 248200), but STGD4 is inherited as an autosomal dominant trait (summary by Kniazeva et al., 1999). For a general phenotypic description and a discussion of genetic heterogeneity of Stargardt disease, see STGD1 (248200).

Age-related macular degeneration (ARMD) is a progressive degeneration of photoreceptors and underlying retinal pigment epithelium (RPE) cells in the macula region of the retina. It is a highly prevalent disease and a major cause of blindness in the Western world. Drusen, pale excrescences of variable size, and other deposits accumulate below the RPE on the Bruch membrane; clinical and histopathologic investigations have shown that these extracellular deposits are the hallmark of early ARMD. As ARMD advances, areas of geographic atrophy of the RPE can cause visual loss, or choroidal neovascularization can occur to cause wet, or exudative, ARMD with accompanying central visual loss (summary by De et al., 2007). Genetic Heterogeneity of Age-Related Macular Degeneration ARMD2 (153800) is associated with mutation in the ABCR gene (601691) on chromosome 1p, and ARMD3 (608895) is caused by mutation in the FBLN5 gene (604580) on chromosome 14q31. Up to 50% of the attributable risk of age-related macular degeneration (ARMD4; 610698) appears to be explained by a polymorphism in the CFH gene (134370.0008). ARMD5 (613761) and ARMD6 (613757) are associated with mutation in the ERCC6 (609413) and RAX2 (610362) genes, respectively. ARMD7 (610149) and ARMD8 (613778), which both represent susceptibility linked to chromosome 10q26, are associated with single-nucleotide polymorphisms in the HTRA1 (602194) and ARMS2 (611313) genes, respectively. ARMD9 (611378) is associated with single-nucleotide polymorphisms in the C3 gene (120700). ARMD10 (611488) maps to chromosome 9q32 and may be associated with a polymorphism in the TLR4 gene (603030). ARMD11 (611953) is association with variation in the CST3 gene (604312); ARMD12 (613784) with variation in the CX3CR1 gene (601470); and ARMD13 (615439) with variation in the CFI gene (217030). ARMD14 (615489) is associated with variation in or near the C2 (613927) and CFB (138470) genes on chromosome 6p21. ARMD15 (615591) is associated with variation in the C9 gene (120940). There is evidence for a form of ARMD caused by mutation in the mitochondrial gene MTTL1 (590050). A haplotype carrying deletion of the complement factor H-related genes CFHR1 (134371) and CFHR3 (605336) is also associated with reduced risk of ARMD. Lotery and Trump (2007) reviewed the molecular biology of age-related macular degeneration and tabulated the genes associated with ARMD, including those with only positive findings versus genes for which conflicting results have been found.

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

Pseudoxanthoma elasticum (PXE) is a systemic disorder that affects the elastic tissue of the skin, the eye, and vascular system. Individuals most commonly present with angioid streaks of the retina found on routine eye examination or associated with retinal hemorrhage and/or characteristic papules in the skin. The most frequent cause of morbidity and disability in PXE is reduced vision due to complications of subretinal neovascularizations and macular atrophy. Other manifestations include premature gastrointestinal angina and/or bleeding, intermittent claudication of arm and leg muscles, stroke, renovascular hypertension, and cardiovascular complications (angina/myocardial infarction). Most affected individuals live a normal life span.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the PROM1 gene.

Age-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.\n\nAge-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.\n\nResearchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.\n\nIn 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.

The 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\nThere 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\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.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the TTC8 gene.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the ZNF513 gene.

In 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.\n\nResearchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.\n\nAge-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.\n\nAge-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the CNGB1 gene.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the GUCA1B gene.

Age-related macular degeneration-2 (ARMD2) is a complex disorder characterized by the accumulation of drusen in and under the retinal pigment epithelium (RPE) and the progressive atrophy of the macular RPE. These changes result in loss of photoreceptor function and vision impairment. Environmental risk factors include cigarette smoking, diet, and cholesterol level (summary by Allikmets et al., 1997). For a general phenotypic description and a discussion of genetic heterogeneity of age-related macular degeneration, see 603075.

Age-related macular degeneration (ARMD) is a multifactorial disorder of the central retina that is the most prevalent cause of progressive vision loss in the developed world. As in other chronic age-related diseases, most cases result from interplay between multiple environmental and genetic factors, with a resultant spectrum of phenotypes. In rare cases, ARMD may manifest early, but there is an exponential rise in prevalence after the age of 60 years (summary by Pras et al., 2015). For a phenotypic description and a discussion of genetic heterogeneity of age-related macular degeneration (ARMD), see 603075.

Age-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.\n\nAge-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.\n\nResearchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.\n\nIn 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.

Any retinitis pigmentosa in which the cause of the disease is a mutation in the PRPF4 gene.

Senior-Loken syndrome-9 is an autosomal recessive disorder characterized by early-onset nephronophthisis and pigmentary retinopathy. Additional more variable features can include liver defects, skeletal anomalies, and obesity (summary by Bizet et al., 2015). For a phenotypic description and a discussion of genetic heterogeneity of Senior-Loken syndrome, see 266900.

Intellectual developmental disorder and retinitis pigmentosa (IDDRP) is characterized by mild to moderate intellectual disability and typical features of RP. Patients experience reduced night vision, constriction of visual fields, and reduced visual acuity; optic disc pallor, attenuated retinal blood vessels, and bone-spicule pigmentation are seen on funduscopy. Attention-deficit/hyperactivity disorder is observed in some patients (Tatour et al., 2017).

CRDHL1 is characterized by cone-rod dystrophy and sensorineural hearing loss, with relatively late onset of both ocular and hearing impairment. The funduscopic findings are characteristic, showing ring-shaped atrophy along the major vascular arcades that manifests on fundus autofluorescence as a hypoautofluorescent band along the vascular arcades surrounded by hyperautofluorescent borders (Namburi et al., 2016). Genetic Heterogeneity of Cone-Rod Dystrophy and Hearing Loss CRDHL2 (618358) is caused by mutation in the CEP250 gene (609689) on chromosome 20q11.

Retinitis pigmentosa-88 (RP88) is characterized by night blindness and constriction of peripheral visual fields, with mildly reduced visual acuity. Examination shows typical findings of RP, including attenuated retinal vessels, pale optic discs, and pigment deposits in the peripheral retinal pigment epithelium (Zobor et al., 2018; Hu et al., 2019; Albarry et al., 2019). For a discussion of genetic heterogeneity of RP, see 268000.

Demyelinating Charcot-Marie-Tooth disease-1H (CMT1H) is an autosomal dominant peripheral sensorimotor neuropathy with onset usually in adulthood (third to fifth decades). Affected individuals present with foot deformities, upper or lower limb sensory disturbances, and motor deficits, mainly impaired gait. Of note, many patients complain of unpleasant sensory sensations in the upper extremities and hands. The disorder is slowly progressive and becomes more apparent with age, although patients usually remain ambulatory. Other features include hypo- or areflexia, limb muscle weakness, and impaired gait. Electrophysiologic studies are consistent with a demyelinating polyneuropathy. Rare patients may have hyperelastic skin or develop age-related macular degeneration (summary by Auer-Grumbach et al., 2011 and Safka Brozkova et al., 2020) For a discussion of genetic heterogeneity of autosomal dominant Charcot-Marie-Tooth disease type 1, see CMT1B (118200).

Mitochondrial DNA depletion syndrome-20 (MTDPS20) is an autosomal recessive multisystem disorder with variable manifestations and severity. Most patients develop symptoms in childhood, although the onset can range from infancy to the teenage years. Prominent features include severe gastrointestinal dysmotility often requiring parenteral nutrition, neurogenic bladder, and muscle weakness and atrophy. Neurologic involvement manifests as headaches, stroke-like episodes, seizures, pyramidal signs, and learning difficulties or cognitive decline. Brain imaging usually shows diffuse leukoencephalopathy and may show cerebellar atrophy. The disorder results from a defect in the maintenance and repair of mitochondrial DNA, resulting in mtDNA depletion and impaired mitochondrial function (summary by Bonora et al., 2021). For a discussion of genetic heterogeneity of mtDNA depletion syndromes, see MTDPS1 (603041).

Cone-rod dystrophy-24 (CORD24) is characterized by night blindness, defective color vision, and reduced visual acuity. Macular atrophy, macular pigmentation deposits, and drusen-like deposits in the macula have been observed. Age at onset varies widely, from the first to the sixth decades of live (Kobayashi et al., 2000; Huang et al., 2013; Zenteno et al., 2023). For a general phenotypic description and discussion of genetic heterogeneity of CORD, see CORD2 (120970).

Retinitis pigmentosa-97 (RP97) is characterized by onset of night blindness and visual field defects in the first decade of life, with later onset of reduced visual acuity (Kong et al., 2023). For a general phenotypic description and a discussion of genetic heterogeneity of RP, see 268000.