Clinical and genetic study of a Chinese family with spinocerebellar ataxia type 7

Spinocerebellar ataxia 7 (SCA7) is a rare disease, and only few SCA7 families have been reported, especially from East Asia. Clinical features of a genetically confirmed SCA7 Chinese family were evaluated. The onset of the disease varied from 4 years to 48 years, and the initial presenting feature was cerebellar ataxia or visual impairment, or both. There were abnormal findings on fundus photography, electroretinogram, flash visual evoked potential and oscillatory potentials. Abnormal mitochondria were also found in skeletal muscle or liver biopsies. The number of cytosine adenine guanine (CAG) repeats ranged from 50 to 97, and the length of CAG repeat was inversely correlated with the age of onset (r=-0.867, P=0.025). Conclusion: The clinical manifestations and SCA7 gene of SCA7 patients were homogeneous in this study. Larger CAG repeats had not only resulted in earlier onset, but also related to the rapid progression and severity of the disease. Abnormal mitochondria may be a common finding in biopsy studies of various organs in SCA7 patients.