The purposes of this study are to identify the gene or genes responsible for an inherited form of Parkinson's disease and learn more about how the disease develops.

In Parkinson's disease, a deficiency of a brain chemical called dopamine impairs the function of the part of the brain that controls movement. As a result, patients may have difficulty moving or they may have uncontrolled movements of their hands and fingers. Parkinson's disease usually occurs sporadically, with no known cause. In a few families, however, the disease seems to be inherited through a gene mutation (change). There is a 50-50 chance that a parent with the mutated gene will pass it on to a child. Children who do inherit the abnormal gene may or may not go on to actually develop Parkinson's disease-the relative chance of this happening is not known.

Individuals 18 years of age and older from families in which Parkinson's disease appears to be inherited may be eligible for this study. Participants will have their medical records reviewed, provide a personal and family medical history (by telephone or in person), and have a small blood sample (2 tablespoons) taken for genetic studies. The total time required for the study is about 1 to 2 hours.

Participants are encouraged to meet with a NIH investigator or with a genetics specialist in their local area before testing to talk about the possible implications for themselves and their families of the test results....