OBJECTIVETo assess the frequency of spinocerebellar ataxia (SCA), including the subtypes of SCA1, SCA2, SCA3/Machado-Joseph disease(MJD), SCA6, SCA7, SCA8, SCA10, SCA12, SCA14, SCA17 and dentatorubro-pallidoluysian atrophy (DRPLA) in Han population in the Chinese mainland, and to specifically characterize the mainland Chinese patients with SCA6 in terms of clinical and molecular features.

METHODSUsing a molecular approach, the authors investigated SCA in 120 families with dominantly inherited ataxias and in 60 patients with sporadic ataxias. Clinical and molecular features of SCA6 were further characterized in 13 patients from 4 families.

RESULTSSCA3/MJD was the most common type of autosomal dominant SCA in the Han population, 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(0), SCA14 (0), SCA17(0) and DRPLA(0). The genes responsible for 41(34.2%) of dominantly inherited SCA families remained undetermined. Among the 60 patients with sporadic ataxias in the present series, 3(5.0%) were found to harbor SCA3 mutations while none were found to harbor SCA6 mutations. In the 4 families with SCA6, significant anticipation was found with no genetic instability on transmission.

CONCLUSIONThe present authors firstly found and reported a geographic cluster of families with SCA6 subtype in the Chinese mainland, which were initially identified in Hans reported of the Chinese mainland.