Huntington's disease is a rare condition that causes parts of the brain to break down, or degenerate. It is also called Huntington's chorea. The disease causes rapid, jerky body movements and the loss of normal mental abilities (dementia). The disease can cause personality changes, behavior problems, and memory loss. Symptoms of the disease usually develop after age 40. There is no known cure for the disease. Treatment with medicines may help control the involuntary movements and behavior changes.

Huntington's disease is caused by a changed, or mutated, gene. If you have a parent with the disease, you have a 50% chance of getting the changed gene and the disease. But there is no way to know when you will develop Huntington's disease. Some people may pass on the changed gene to a child before knowing that they have the changed gene.

A blood test can show whether you have the changed gene. You may want to have genetic counseling if you are thinking of having the test. Genetic counselors are experts who can explain what the test means, tell you the benefits and risks of the test, and answer your questions. But you make the decision about whether to have the test.