Huntington disease (HD) is a progressive disorder causing motor, cognitive, and psychiatric disturbances, with a mean age at onset of 35 to 44 years and a median survival time of 15 to 18 years.1 Although most cases have the classic triplet repeat expansion, HD specialists all follow up patients who have all the cardinal features of HD but do not have the HD mutation. These cases are problematic because genetic counseling is difficult, the prognosis is uncertain, and the fear is that a potentially treatable condition may be missed.
Dupré N, Rouleau G. The Puzzle of Huntington Disease Phenocopies. JAMA Neurol. 2016;73(9):1056-1058. doi:10.1001/jamaneurol.2016.2095