Although follow-up genetic studies are inconsistent for some of these genes or conclusive data are still pending, ample evidence for a causal association was obtained for PD with five genes, that is, α-synuclein (SNCA; MIM] 163890), parkin (PARK2; MIM] 602544), PTEN-induced putative kinase 1 (PINK1; MIM] 608309), DJ-1 (PARK7; MIM] 602533), and Leucine-rich repeat kinase 2 (LRRK2; MIM] 609007). Here, SNCA is linked to Parkinson disease.