ATXN2 and cerebellar ataxia: Long polyglutamine (polyQ) repeats (CAG trinucleotide repeat expansions) in the ataxin-2 (ATXN2) gene may cause spinocerebellar ataxia [69], but intermediate polyQ repeats (27 to 33 CAG trinucleotide repeat expansions) have been associated with sporadic ALS [70].