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.

Retinitis pigmentosa-10 (RP10) is characterized in most patients by early onset and rapid progression of ocular symptoms, beginning with night blindness in childhood, followed by visual field constriction. Some patients experience an eventual reduction in visual acuity. Funduscopy shows typical changes of RP, including optic disc pallor, retinal vascular attenuation, and bone-spicule pattern of pigmentary deposits in the retinal midperiphery. Electroretinography demonstrates equal reduction in rod and cone responses (Jordan et al., 1993; Bowne et al., 2002; Bowne et al., 2006). For a general phenotypic description and a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000.

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

SHILCA is characterized by early-onset retinal degeneration in association with sensorineural hearing loss, short stature, vertebral anomalies, and epiphyseal dysplasia, as well as motor and intellectual delay. Delayed myelination, leukoencephalopathy, and hypoplasia of the corpus callosum and cerebellum have been observed on brain MRI (Bedoni et al., 2020).