CACNA1A and Huntington disease: To date, this group includes the distinct Spinocerebellar Ataxias (SCA1, SCA2, SCA3/Machado–Joseph disease, SCA6, SCA7 and SCA17) [3–5], dentatorubral-pallidoluysian atrophy (DRPLA), Huntington disease (HD), and most recently, Huntington disease-like 2 (HDL2) [6].