ATXN2 and Huntington disease: Thus, SCA2 belongs to a group of polyglutamine (polyQ) disorders including several other spinocerebellar ataxias (SCA1, SCA3, SCA6, SCA7, and SCA17), Huntington’s disease (HD), Dentatorubral-pallidoluysian atrophy (DRPLA), and Spinal and bulbar muscle atrophy (SBMA) [17, 18].