Late adult-onset autosomal recessive retinopathy secondary to homozygous CLN3 c.175G>A mutation: A case report

A 60-year-old female presented with progressive intermittent blurred vision in the temporal field and mild nyctalopia. Visual acuity was 6/15 in both eyes, with bilateral perifoveal hyperautofluorescent rings and loss of outer retinal layers. Genetic testing identified a homozygous pathogenic variant in the CLN3 gene (c.175G>A p.(Ala59Thr)). In the left fovea, cystoid spaces were treated with topical brinzolamide and oral acetazolamide. The visual acuity improved to 6/12, and macular edema improved. This case highlights the value of genetic testing in adult-onset maculopathy, shows an atypical presentation of CLN3 mutation, and supports carbonic anhydrase inhibitors to manage dystrophic macular edema. This is the first report of a homozygous CLN3 c.175G>A mutation presenting with an isolated generalised retinal dystrophy with a retinitis pigmentosa phenotype in a middle-aged adult.