The genetics of Parkinson's disease and parkinsonian syndromes.

The finding of a mutation in the alpha-synuclein gene in a rare autosomal dominant form of idiopathic Parkinson's disease (IPD), has prompted increased interest in identifying genes that account for the more common sporadic form. A number of association studies have suggested that functional polymorphisms in genes that play a role in dopamine, drug and toxin metabolism may increase the relative risk of IPD. Unfortunately, patient numbers are often small, and the results have not been consistently reproduced. This article reviews the evidence from epidemiological, imaging and genetic studies to determine the role of genetic susceptibility in IPD and parkinsonian syndromes.