Tay-Sachs disease is a hereditary disorder of the nervous system. It occurs chiefly among Jewish children of eastern European ancestry. Tay-Sachs disease causes severe brain damage, enlargement of the head, convulsions, blindness, deafness, lack of energy, and eventually death. Victims develop a reddish spot on the retina of the eye. They begin to have symptoms when they are about 6 months old. There is no treatment for Tay-Sachs disease. Most victims live for only three or four years.