Huntington's chorea, or Huntington's disease, is a hereditary disorder affecting about 1 in every 10,000 persons. It is characterized by irregular movements of the body, slurred speech, and a progressive deterioration of mental functioning. Brain damage takes place in the basal ganglia, a region of the cerebrum; nerve cells die, and two neurotransmitters produced by these cells are depleted in the brain. At the same time, an excess of another neurotransmitter, dopamine, builds up in the basal ganglia. The damage causes alternating periods of excitement and depression, sometimes misdiagnosed as schizophrenia.

If one of the parents of a child has Huntington's chorea and the other does not, the child has a 50 percent chance of inheriting the disease; once it is transmitted, it is certain to develop. The first symptoms usually appear between the ages of 35 and 55, but earlier and later occurrences are also known. The disease may progress for 10 to 20 years until the patient dies.

No treatment yet exists for Huntington's chorea. During the 1980s, however, genetic markers (identifiable segments of the DNA molecule) were discovered that can be used as indicators of the presence of the gene--as yet unidentified--that causes the disease. In 1988, Canada initiated the world's first nationwide screening program--on a voluntary basis--for adults at risk for Huntington's chorea.

Peter L. Petrakis
Bibliography: Hayden, M.R., Huntington's Chorea (1984); Phillips, D.H., Living with Huntington's Disease (1982); Roberts, Leslie, "Huntington's Gene," Science, Feb. 9, 1990.