SCA31 is a common ataxia in Japan (Onodera, 2006; Ouyang et al., 2006; Basri et al., 2007; Hayashi et al., 2007; Nozaki et al., 2007; Yoshida et al., 2009), whereas it is very rare in surrounding parts of Asia such as Korea, Taiwan, and China (Lee et al., 2007, 2012; Ouyang et al., 2012; Pedroso et al., 2015) and extremely rare in Caucasian populations (Ishikawa et al., 2011). Here, TK2 is linked to Ataxia.