ATXN2 and Ataxia: For ataxias SCA1, SCA2, SCA3, SCA6, SCA7, SCA17 and dentatorubral-pallidoluysian atrophy, expansion beyond 39, 33, 45, 20, 34, 41, and 35 repeats in the ATXN1, ATXN2, ATXN3, CACNA1A, ATXN7, TBP, and ATN1 genes, respectively, will cause disease.