Associated Features Supporting Diagnosis
Depression, irritability, anxiety, obsessive -compulsive symptoms, and apathy are fre-
quently, and psychosis more rarely, associat ed with Huntington’s disease and often pre-
cede the onset of motor symptoms.
Prevalence
Neurocognitive deficits are an eventual ou tcome of Huntington’s disease; the worldwide
prevalence is estimated to be 2.7 per 100,000.  The prevalence of Huntington’s disease in
North America, Europe, and Australia is 5.7 pe r 100,000, with a much lower prevalence of
0.40 per 100,000 in Asia. 
Development and Course
The average age at diagnosis of Huntington’s disease is approximately 40 years, although
this varies widely. Age at onset is inversely correlated with CAG expansion length. Juve-
nile Huntington’s disease (ons et before age 20) may present more commonly with brady-
kinesia, dystonia, and rigidity than with the choreic movements characteristic of the adult-
onset disorder. The disease is gradually progre ssive, with median survival approximately
15 years after motor symptom diagnosis.
Phenotypic expression of Huntington’s diseas e varies by presence of motor, cognitive,
and psychiatric symptoms. Psychiatric and co gnitive abnormalities can predate the motor
abnormality by at least 15 years. Initial symp toms requiring care often include irritabity,
anxiety, or depressed mood. Other behavioral  disturbances may include pronounced ap-
athy, disinhibition, impulsivit y, and impaired insight, with apathy often becoming more
progressive over time. Early movement symptoms may involve the appearance of fidget-
iness of the extremitie s as well as mild apraxia  (i.e., difficulty with purposeful movements),