Inherited retinal diseases (IRDs) comprise a phenotypically and genetically heterogeneous group of ocular disorders that cause visual loss via progressive retinal degeneration. Here, we report the genetic characterization of 1210 IRD pedigrees enrolled through the Japan Eye Genetic Consortium and analyzed by whole exome sequencing. The most common phenotype was retinitis pigmentosa (RP, 43%), followed by macular dystrophy/cone- or cone-rod dystrophy (MD/CORD, 13%). In total, 67 causal genes were identified in 37% (448/1210) of the pedigrees. The first and second most frequently mutated genes were EYS and RP1, associated primarily with autosomal recessive (ar) RP, and RP and arMD/CORD, respectively. Examinations of variant frequency in total and by phenotype showed high accountability of a frequent EYS missense variant (c.2528G>A). In addition to the two known EYS founder mutations (c.4957dupA and c.8805C>G) of arRP, we observed a frequent RP1 variant (c.5797C>T) in patients with arMD/CORD.

Table S2. ABCA4 variant categorization:

Finally, we examined whether the phenotype‐associated known/candidate pathogenic variants could explain the patient's disease, andif the MAF in population‐matched control data (8.3kJPN) was relatedto disease prevalence. Patients were classified as “Solved” if theirgenotype was consistent with their clinical phenotype. Patients wereclassified as “Partially solved” when a heterozygous known/candidatepathogenic variant was detected in a recessive allele, but without anadditional variant in trans. Patients were categorized as “Unsolved” iftheir genotypes exhibited either no candidate pathogenic variants ormultiple heterozygous pathogenic variants that did not explain thephenotype clearly. Variants annotated as causal for solved patients arelisted in Supporting Information: Table S2. Novel variants identified inthis study are listed in the second sheet of Table S2. SupportingInformation: Table S3 shows the phenotypes and genotypes of solvedpatients.