Clinical neurogenetics: huntington disease.

Huntington disease (HD) is an autosomal dominant, adult-onset, progressive neurodegenerative disease characterized by the triad of abnormal movements (typically chorea), cognitive impairment, and psychiatric problems. It is caused by an expanded CAG repeat in the gene encoding the protein huntingtin on chromosome 4 and causes progressive atrophy of the striatum as well as cortical and other extrastriatal structures. Genetic testing has been available since 1993 to confirm diagnosis in affected adults and for presymptomatic testing in at-risk individuals. This review covers HD signs, symptoms, and pathophysiology; current genetic testing issues; and current and future treatment strategies.