Knowledge about genes in familial parkinsonism helps elucidate idiopathic disease

Parkinson's disease is a neurodegenerative disorder in which loss of dopaminergic cells in the pars compacta of the substantia nigra is recognised to be a central pathological event. Despite several decades of intensive research, however, its cause remains unknown. Although not usually thought of as a hereditary disorder, accumulating evidence suggests a significant genetic component for susceptibility to idiopathic Parkinson's disease. Population based epidemiological studies indicate that the risk of Parkinson's disease is at least doubled in first degree relatives of patientscompared with controls, while hospital based studies suggest a higher risk. 1 2 The lifetime risk in first degree relatives of sporadic cases is estimated to be as high as 17%.3

A molecular genetic approach to the study of Parkinson's disease has been hampered by the relative scarcity of large kindreds with familial Parkinson's disease and the difficulty of obtaining DNA for analysis from more than one generation in this late onset disorder. Despite these difficulties this approach has finally begun to bear fruit. By using as a starting point families in which parkinsonism is clearly inherited as a mendelian trait, three genes for Parkinson's disease have recently been characterised.4^–6 …