USC researchers have identified a family with an inherited form of Parkinson's disease, providing further evidence that the disorder has a genetic component. New Jersey researchers reported last year on the discovery of the first family with such a history of the disease, which is characterized by tremors, rigidity of the limbs and, often, mental impairment. It affects as many as 1.5 million Americans.
The cause of Parkinson's is unknown, but recent research has hinted that chemicals in the environment, or perhaps even bacteria, may play a contributing role. The importance of genetic susceptibility has been a mystery, however.