There are nine known polyQ diseases including Huntington’s disease (HD), six spinocerebellar ataxias, namely SCA1, SCA2, SCA3, SCA6, SCA7 and SCA17, dentatorubral-pallidoluysian atrophy (DRPLA) and spinal and bulbar muscular atrophy (SBMA). The gene discussed is CACNA1A; the disease is dentatorubral-pallidoluysian atrophy.