Ocular phenotype of Bothnia dystrophy, an autosomal recessive retinitis pigmentosa associated with an R234W mutation in the RLBP1 gene

Objective: To describe the phenotype of Bothnia dystrophy, an autosomal rec essive retinal dystrophy with an R234W mutation in the RLBP1 gene encoding cellular retinaldehyde-binding protein. Design: Medical records were reviewed retrospectively. Ophthalmologic exami nation, including kinetic perimetry and, in selected cases, adaptometry, co lor vision tests, fluorescein angiography, and electrophysiologic studies, was performed. The study included 24 individuals, all homozygous for an R23 4W mutation in the RLBP1 gene. Results: Patients typically show night blindness from early childhood. In y oung adults, retinitis punctata albescens was observed, followed by macular degeneration and a decrease in visual acuity that led to legal blindness i n early adulthood. Dark adaptometry and electrophysiologic testing showed a n initial loss of rod function followed by a progressive reduction of the c one responses in older ages. Conclusions: Bothnia dystrophy is a unique retinal dystrophy belonging to t he rod-cone dystrophies and has a high prevalence in northern Sweden. Fifty -seven cases of Bothnia dystrophy have been diagnosed, indicating a prevale nce as high as 1 per 4500 population in the geographic area studied. A defe ct ability of mutated cellular retinaldehyde-binding protein to bind retino id probably explains the defect rod function followed by central and periph eral degeneration. Clinical Relevance: Retinal dystrophies associated with other mutations of the RLBP1 gene, including retinitis pigmentosa of Bothnia type, might accou nt fur a considerable number of cases of autosomal recessive retinitis pigm entosa in other geographic areas as well.