Hereditary ataxias may be autosomal‐dominant diseases, including forms of spinocerebellar ataxia (SCA), several of which are associated with polyglutamine repeats in the dysfunctional protein; for example: ataxin 1 in SCA1; ataxin 2 in SCA2; Cacna1a encoding the voltage‐dependent Ca2+ channel (VDCC) CaV2.1 subunit in SCA6 (also in episodic ataxia 2). The gene discussed is ATXN2; the disease is cerebellar ataxia.