Spinocerebellar ataxia type 6 in Mainland China: molecular and clinical features in four families.

The hereditary spinocerebellar ataxias (SCAs) are a clinically and genetically heterogeneous group of neurodegenerative disorders. The genes causing 11 of these diseases have been identified. To date, there is no report of SCA type 6 (SCA6) in Mainland Chinese. Using a molecular approach, we investigated SCA6 as well as other SCA subtype in 120 Mainland Chinese families with dominantly inherited ataxias and in 60 Mainland Chinese patients with sporadic ataxias. Clinical and molecular features of SCA6 were further characterized in 13 patients from 4 families. We found that SCA3/MJD was the most common type of autosomal dominant SCA in Mainland Chinese, accounting for 83 patients from 59 families (49.2%), followed by SCA2 (8 [6.7%]), SCA1 (7 [5.8%]), SCA6 (4 [3.3%]), SCA7 (1 [0.8%]), SCA8 (0%), SCA10 (0%), SCA12 (1 [0.8%]), SCA14 (0%), SCA17 (0%) and DRPLA (0%). The genes responsible for 40 (33.3%) of dominantly inherited SCA families remain to be determined. Among the 60 patients with sporadic ataxias in the present series, 3 (5.0%) were found to harbor SCA3 mutations, whereas none were found to harbor SCA6 mutations. In the 4 families with SCA6, we found significant anticipation in the absence of genetic instability on transmission. This is the first report of geographic cluster of families with SCA6 subtype in Mainland China.