While several candidate genes like LRRK2 (MIM# 609007), SNCA (MIM# 163890), DJ1 (HUGO-approved symbol PARK7; MIM# 602533), PINK1 (MIM# 608309), and Parkin (HUGO-approved symbol PARK2; MIM# 602544) have been implicated in one or more varieties of familial Parkinsonism [Klein and Schlossmacher, 2007], no single genetic susceptibility factor has yet been shown to consistently increase the risk for PD. This evidence concerns the gene PRKN and Parkinson disease.