Spinocerebellar ataxia type 3 (SCA3), an autosomal dominant cerebellar ataxia caused by abnormal expansion of cytosine‐adenine‐guanine (CAG) repeats in ATXN3 gene (MIM: 109150) (Kawaguchi et al., 1994), is regarded as the most common SCA subtype in China (Gan et al., 2010). The gene discussed is ATXN3; the disease is Spinocerebellar ataxia type 3.