Two novel genetic associations with sector retinitis pigmentosa: USH2A and PRPF31

Sector retinitis pigmentosa (RP) is an attenuated phenotype in comparison to classic pan-retinal disease. The inferior retina is most often affected, though other quadrants may become involved with time, particularly with more damaging genetic variants. Sector RP has been described in association with several known genotypes, most commonly RHO. Case series of patients with a sector RP phenotype (and any affected family) and review of the literature. We describe two new genetic associations of sector RP: USH2A and PRPF31. Proband 1 had sector RP due to homozygous USH2A:c.13274C>T’ variants while proband 2 had sector RP due to a heterozygous PRPF31:c.351dup variant. There was significant intrafamilial variability in each pedigree. Though both variants are previously reported, the phenotype in those reports was not consistent with sector RP. The current USH2A pedigree is the first reported with the c.13274C>T’ variant homozygously, expressing a restricted, predominantly perivascular, sectoral RP. Non-syndromic USH2 genes have not previously been associated with sector RP. In the PRPF31 pedigree (c.351dup), the proband has restricted/sectoral disease but her daughter has classic pan-retinal RP. The cause of the attenuated phenotype and intrafamilial variability is unknown but could depend on several factors including occult modifier genes and environmental influences (e.g. light exposure to the inferior retina).