The disease is caused by a defect in a gene on chromosome number 4. This gene is known as the Huntington disease (HD) gene.
Huntington's disease is almost always an inherited disease, passed from parent to child through a genetic mutation. Each child of a parent with the condition has a 50-50 chance of inheriting the Huntington disease gene.
If a child does not inherit the Huntington disease gene, he or she will not develop the condition and cannot pass it to subsequent generations.
A person who inherits the HD gene will sooner or later develop Huntington's disease. Whether one child inherits the gene has no bearing on whether others will or will not inherit it.
Not all cases of Huntington's disease are inherited; 1 to 3 percent of cases are sporadic, meaning they occur even though there is no family history.
(Click Cause of Huntington's Disease to learn more about the HD gene.)
Early symptoms of Huntington's disease may include:
- Mood swings
- Trouble driving, learning new things, remembering a fact, or making a decision.
As the disease progresses, concentration on intellectual tasks becomes increasingly difficult, and people may have difficulty feeding themselves and swallowing.
Some of the symptoms for juvenile Huntington's disease differ from those of the adult-onset form.
(Click Symptoms of Huntington Disease for more information.)