Genetic Susceptibilities in Parkinson’s Disease

The current understanding of PD includes a long initial
phase, often dubbed ‘‘preclinical,’’ in which non–movement disorder
symptoms are common but heterogeneous in presentation. Early twin studies suggest that genetic susceptibilities might not play a large role in PD etiology. More
recent studies show that, in some populations, a single point
mutation in the LRRK2 gene causes more than one third of PD
cases, with the ancient G2019S mutation reported at a higher
frequency in patients without knowledge of PD in their family
than in patients aware of a family history of disease, in some
populations. Genetic studies have therefore illuminated
specific causes of PD that promise to aid in the delineation
of pathogenesis and the development of therapeutics.