CACNA1A and Huntington disease: To date, nine disorders have been reported, including spinal and bulbar muscular atrophy (SBMA), Huntington’s disease (HD), several spinocerebellar ataxias (SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17), and dentatorubral pallidoluysian atrophy (DRPLA)95.