Retinitis Pigmentosa 77

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2019-09-22
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A number sign (#) is used with this entry because of evidence that retinitis pigmentosa-77 (RP77) is caused by homozygous or compound heterozygous mutation in the REEP6 gene (609346) on chromosome 19p13.

For a general phenotypic description and a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000.

Clinical Features

Arno et al. (2016) examined the probands from 5 unrelated families with autosomal recessive retinitis pigmentosa. All probands presented with nyctalopia, with onset varying from early childhood to 20 years of age. There was a gradual decline in vision, characterized by reduced peripheral visual fields followed by reduced visual acuity. At last review (ages 20 to 54 years), visual acuity ranged from 20/30 to 20/400, and all patients had significantly constricted visual fields, ranging from less than 10 degrees to 30 degrees. Four probands also had posterior subcapsular cataracts that required surgery in 2 cases. Fundus examination revealed attenuated retinal vessels and midperiphery pigmentary mottling due to atrophy of the retinal pigment epithelium; 4 probands also showed intraretinal pigmentary migration ('bone spicules'). OCT imaging of the macula demonstrated outer retinal atrophy with centrally preserved inner segment ellipsoid bands, and 2 probands had cystoid macular edema. Fundus autofluorescence imaging revealed parafoveal rings of increased autofluorescence and widespread loss of autofluorescence in the midperiphery, which showed nummular features in 3 affected individuals. Electrophysiologic testing in 3 probands showed severe generalized retinal dystrophy, with severely reduced or undetectable responses in 2 individuals in their thirties and severe cone-rod dystrophy in 1 patient at age 15 years. Arno et al. (2016) concluded that the clinical findings were consistent with a diagnosis of RP.

Molecular Genetics

By whole-exome sequencing in 2 probands with RP who were negative for mutation in 176 and 226 retinal disease-associated genes, respectively, as well as by whole-genome sequencing in 599 probands with inherited retinal disease and direct Sanger sequencing in a panel of 400 RP-affected individuals who were negative for mutation in 192 known RP-associated genes, Arno et al. (2016) identified affected individuals from 5 families with homozygous or compound heterozygous mutations in the REEP6 gene (see, e.g., 609346.0001-609346.0004).