ABSTRACT
For many years, Parkinson’s disease (PD) was thought to be strictly inŸuenced by environmental factors without a substantial genetic contribution to disease etiology. However, studies from around the world have provided evidence that genetic risk factors are involved in the pathogenesis of the idiopathic form of PD. Estimates of the relative risk to rstdegree relatives of an affected individual range from 2.7 to 3.5 in the United States,1,2 2.9 in Finland,3 6.7 in Iceland,4 7.7 in France,5 3.2 in three centers within Europe,6 5.0 in Canada,7 13.4 in Italy,8 and 7.1 in Germany.9
