Autosomal recessive spinocerebellar ataxias in Japan

Recent new sequencing techniques allow the identification of novel responsible genes for autosomal recessive spinocerebellar ataxias (ARCAs). However, the same phenotypes are sometimes attributed to the different responsible genes in ARCAs. On the contrary, the same responsible genes may cause heterogeneous phenotypes with respect to the age at onset, symptoms, and the severity of the disease progression. In addition, it is an important issue to clarify whether the gene mutations identified in Caucasian patients with infantile-onset ARCAs are also observed in Japanese patients with adult-onset ARCAs. In this article we review the characteristics of several ARCAs, the existence of which has been recently identified or confirmed in Japan.