TBP and cerebellar ataxia: Spinocerebellar ataxia (SCA) type 17-digenic TBP/STUB1 disease (SCA17-DI) has been recently segregated from SCA17, caused by digenic inheritance of two gene mutations – intermediate polyglutamine-encoding CAG/CAA repeat expansions (polyQ) in TBP (TBP41 − 49) and STUB1 heterozygosity – the former being associated with SCA17, and the latter with SCA48 and SCAR16 (autosomal recessive).