Huntington's chorea is a hereditary disease that is marked by chronic, progressive chorea and marked mental deterioration in middle life, usually in the fourth decade.
The disease has a prevalence of about 1 in 20,000 in the UK. It is inherited as an autosomal dominant trait with full penetrance. The family history of the disease is often concealed.
The gene responsible for this condition resides on chromosome 4. Predictive DNA testing of at risk relatives of sufferers reduces anxiety, whatever the test outcome.