Huntington’s chorea is an incurable, autosomal dominant inherited disorder, with onset as an adult, associated with loss in specific subsets of neurons in the basal ganglia and cortex. This disorder is characterized by involuntary movements, dementia, and behavioral changes.

The frequency of Huntington’s chorea varies significantly, depending on the particular country or region.

Frequency of Huntington’s Chorea by Country/Region

Country/Region	Incidence
United States	4.1-8.4:100,000
Lake Maracaibo, Venezuela	700:100,000
Mauritius (off South Africa)	46:100,000
Tasmania	17.4:100,000
Europe (most)	1.63-9.95:100,000
Finland	<1:100,000
Japan	<1:100,000

The gene for Huntington’s chorea, designated IT15, is found on chromosome 4p. Selective neuronal dysfunction and loss of neurons may be explained by several mechanisms, such as excitotoxicity, oxidative stress, impaired energy metabolism, and apoptosis. One theory is that polyglutamine repeats cause neuronal degeneration through interactions with other proteins containing short polyglutamine tracts.

The duration of this disorder is quite variable, but the mean duration is about 19 years. Survival is generally 10 to 25 years after the onset of the illness.

This disorder afflicts both genders without preference. In general, onset occurs between the ages of 35 to 44 years, with a range from 2 years of age to more than 80 years. Onset of this disorder earlier than 10 years of age or later than 70 years is not unheard of, but is rare.