Huntington disease

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Huntington disease is a hereditary disease that begins with occasional involuntary jerking or spasms, then progresses to more pronounced involuntary movements (chorea and athetosis), mental deterioration, and death.

In Huntington disease, parts of the brain that help smooth and coordinate movements degenerate.
Movements become jerky and uncoordinated, and mental function, including self-control and memory, deteriorates.
Doctors base the diagnosis on symptoms, family history, imaging of the brain, and genetic testing.
Drugs can help relieve the symptoms, but the disorder is progressive, ultimately ending in death.

(See also Overview of Movement Disorders.)
Huntington disease affects 1 to 10 of 100,000 people. The number of people affected varies depending on which part of the world they live in. It affects both sexes equally.
The gene for Huntington disease is dominant. That is, having only one copy of the abnormal gene, inherited from one parent, is sufficient to cause the disease. Therefore, children of a person who has Huntington disease have a 50% chance of developing it.
Huntington disease is caused by gradual degeneration of parts of the basal ganglia called the caudate nucleus and putamen. The basal ganglia are collections of nerve cells located at the base of the cerebrum, deep within the brain. They help smooth out and coordinate movements.