The only point mutation associated with adult-onset ITPR1-associated ataxia (encoding p.Pro1068Leu) is located relatively near in space to another early-onset mutation, and is also predicted to be only mildly destabilizing, suggesting that it might also be associated with a dominant-negative mechanism, rather than the haploinsufficiency associated with SCA15 gene deletions. Here, ITPR1 is linked to cerebellar ataxia.