A recent genetic study has revealed the pathogenesis of the SCA17/HDL phenotype in which intermediate alleles arise through digenic inheritance of two gene mutations – TBP polyQ and a heterozygous STUB1 variant – the latter being associated with SCA48 and the spinocerebellar autosomal recessive type 16 (SCA17-DI) [2]. Here, STUB1 is linked to spinocerebellar ataxia type 17.