C9orf72 and Huntington disease: These HD phenocopies include neurodegenerative diseases caused by repeat expansions in the C9orf72 gene, spinocerebellar ataxia (SCA) 17, Huntington disease-like 2 (HDL2), dentatorubropallidoluysian atrophy (DRPLA), neuroferritinopathy, familial prion disease (e.g. Huntington disease-like 1 [HDL1]) [7].