Huntington's disease

Huntington's disease, hereditary, acute disturbance of the central nervous system usually beginning in middle age and characterized by involuntary muscular movements and progressive intellectual deterioration; formerly called Huntington's chorea. The disease is sometimes confused with chorea or St. Vitus's dance, which is not hereditary. It attacks the cells of the basal ganglia, clusters of nerve tissue deep within the brain that govern coordination.

The onset is insidious and inexorably progressive; no treatment is known. Psychiatric disturbances range from personality changes involving apathy and irritability to bipolar or schizophreniform illness. Motor manifestations include flicking movements of the extremities, a lilting gait, and motor impersistence (inability to sustain a motor act such as tongue protrusion).

In 1993 the gene responsible for the disease was located; within that gene a small segment of code is, for some reason, copied over and over. Genetic counseling is extremely important, since 50% of the offspring of an affected parent inherit the gene, which inevitably leads to the disease.