In Vasterbotten County in northern Sweden an usually high frequency of a distinctive form of retinal dystrophy, termed Bothnia dystrophy, occurs. Burstedt et al. (1999, 2001) described the phenotype. Fifty-seven cases of Bothnia dystrophy were diagnosed, indicating a ... In Vasterbotten County in northern Sweden an usually high frequency of a distinctive form of retinal dystrophy, termed Bothnia dystrophy, occurs. Burstedt et al. (1999, 2001) described the phenotype. Fifty-seven cases of Bothnia dystrophy were diagnosed, indicating a prevalence as high as 1 per 4,500 persons in that particular geographic area. Patients typically showed night blindness from early childhood. In young adults, retinitis punctata albescens (see 136880) was observed, followed by macular degeneration and a decrease in visual acuity that led to legal blindness in early adulthood. Dark adaptometry and electrophysiologic testing showed an initial loss of rod function followed by progressive reduction of the cone responses in older ages. To characterize the clinical phenotype of Bothnia dystrophy, with an emphasis on electrophysiology, Granse et al. (2001) studied 2 unrelated (or at least distantly related) patients of 10 and 11 years of age who had the arg234-to-trp mutation (R234W; 180090.0004) in the RLBP1 gene. They concluded that patients with the R234W mutation may have a normal fundus appearance early in the disease course. Multifocal electroretinograms could be used for the objective documentation of disturbed macular function. The rod response was absent in the electroretinograms of the 2 patients; however, after prolonged dark adaptation (20 to 24 hours), the rods recovered completely. The central cones did not seem to recover.
Burstedt et al. (1999) showed that all 20 patients with Bothnia dystrophy that they studied were homozygous for a C-to-T substitution in exon 7 of the RLBP1 gene, leading to an R234W mutation.