Understanding HD

The symptoms of Huntington disease (HD) appear when an abnormal protein builds up in nerve cells in certain areas of the brain, causing the cells to die. One of the brain areas affected is the area that controls movement. Cells in the outer layer of the brain also die, affecting mental abilities. In 1993, researchers discovered that people with HD have a single altered gene, which somehow triggers this process.

Brain scan from a patient with Huntington disease (right) showing a larger cavity where brain cells have died, compared with a normal brain (left). Department of Neurogenetics, Institute of Neurology, London