Macular degeneration associated with aberrant expansion of trinucleotide repeat of the SCA7 gene in 2 Japanese families

Objective: To evaluate the macular function of Japanese patients with a tri nucleotide repeat expansion in the spinocerebellar ataxia type 7 (SCA7) gen e. Methods: Ophthalmic findings in patients whose DNA analysis revealed expand ed alleles of the trinucleotide repeat in the SCA7 gene were evaluated. Results: Trinucleotide repeat was expanded from 40 to 48 in affected patien ts (control subjects, 12 repeats). Affected patients were characterized by different degrees of visual acuity decrease (0.09-0.9), a tritan axis color vision, a coarse granular appearance of the macular region on scanning las er ophthalmoscopy, depression of multifocal, electroretinograms, and macula r degeneration. However, pigmentary changes were not observed in the retina . The trinucleotide repeat was longer and the onset of macular dysfunction was earlier in the younger generation. One patient in a family manifested d ecreased visual acuity 10 years preceding other neurologic signs. Conclusions and Clinical Relevance: Patients with SCA7 mutations showed mac ular dysfunction or degeneration with expansion of CAG repeat in the SCA7 g ene. However, the lesions were less pigmented than those previously reporte d. Patients also showed ophthalmologic anticipation, which has not been rep orted for the ocular changes in other patients who have trinucleotide repea t expansion of the responsible genes.