A progressive, fatal, autosomal dominant disorder characterized by motor, behavioral, and cognitive dysfunction. Onset is typically between 25 and 45 years. Rapid, nonpatterned, semipurposeful, involuntary choreiform movements are the hallmark feature; dysarthria, gait disturbance, and oculomotor abnormalities also occur. In late stages, chorea becomes less prominent, and the picture is dominated by dystonia, rigidity, bradykinesia, myoclonus, and spasticity. Eventually, behavioral and cognitive disturbances can be a major source of disability. HD is caused by an expansion in the number of polyglutamine (cytosine-adenine-guanine [CAG]) repeats in coding sequence of the HTT gene encoding the protein huntingtin.

• Treatment involves a multidisciplinary approach with medical, neuropsychiatric, social, and genetic counseling for pts and families.
• Dopamine-blocking agents may control the chorea; tetrabenazine may also treat chorea but can cause secondary parkinsonism.
• Depression and anxiety should be treated with appropriate antidepressant and antianxiety drugs.
• Psychosis can be treated with atypical neuroleptic agents.
• No disease-modifying agents currently exist.