Huntington's Disease (HD) is caused by a defective gene which results in the gradual destruction of neurons (brain cells), particularly in those parts of the brain known as the basal ganglia and the cerebral cortex.
The defective gene can be passed from one generation to the next. If a parent has the gene, each child has a 50/50 chance of either inheriting or escaping it.
If a person inherits the defective gene it will eventually become active and brain cells in the body's central nervous system will start to die. This is when a person begins to develop the symptoms of HD.
[This page is based on the Association's publication Huntington's Disease. Originally written by Dennis H. Phillips, Ph.D. and first published in 1981, it has been frequently revised and republished since then. The current edition was published in 2001. (Australian Huntington's Disease Association (NSW) Inc.Huntington's Disease West Ryde, 2001.)]