SCA11 is somewhat unusual among SCAs, in part because the reported causal mutations are base pair insertions or deletions within the coding region of TTBK2 (Houlden et al., 2007; Johnson et al., 2008; Lindquist et al., 2017), rather than the expansion of CAG repeats, which is the genetic cause of most SCA subtypes (Hersheson et al., 2012). The gene discussed is TTBK2; the disease is autosomal dominant cerebellar ataxia.