This family includes dentatorubral-palidoluysian atrophy (DRPLA), caused by polyQ expansion in atrophin 1; [7,8], spinal and bulbar muscular atrophy (SBMA or Kennedy's disease), caused by polyQ expansion in the androgen receptor, AR; [9-11], and spinocerebellar ataxias 1–3, 6, 7, and 17 (SCAs), caused by polyQ expansions in various proteins [1,3]. The gene discussed is ATN1; the disease is Kennedy disease.