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. A faulty gene produces a defective protein attacks neurons in 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.