Natural History of Spinocerebellar Ataxia Type 7 (SCA7)

National Eye Institute

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Abstract

Spinocerebellar Ataxia Type 7 is a neurodegenerative disease caused by an expansion of a CAG trinucleotide repeat in the coding region of the ATXN7 gene. It is distinguished from other autosomal dominant spinocerebellar ataxias by its associated retinal degeneration. Vision loss is therefore a significant comorbidity affecting the quality of life of these patients however at this time, treatment is limited to lifestyle modification. While numerous case reports or small case series have been reported in populations from across the globe, the longitudinal clinical course of retinal degeneration in molecularly-confirmed SCA7 individuals has not been documented in a prospective manner. With this study, we hope to gather this information in anticipation of future clinical trials. Of the 22 participants currently enrolled, age range at baseline visits ranged from 16.9 to 62.8 years, mean 42.4 years. CAG repeat expansion ranges from 40 to 66, with an average of 46 CAG repeats in the expanded allele. Visual acuity at presentation ranged from 20/12.5 to 20/400 with good correlation between eyes. Optic atrophy, cone rod dystrophy and macular atrophy are the key ophthalmic features of SCA7 and noted in our cohort in varying ranges. We have identified both focal macular involvement as well as more diffuse retinal changes on different testing modalities. The enrolled participants have undergone neurologic evaluation as well as neuroimaging which demonstrated a range of cerebellar atrophy. While we continue to establish our cohort of SCA7 patients, we are focused on characterizing the anatomical and functional characteristics of SCA7 patients to advance our understanding of the progression of retinal and neurodegeneration.