While most cases of Parkinson's disease are sporadic (without a known genetic cause), genetic factors play a role in disease susceptibility. Several genes have been implicated in both familial and sporadic forms of PD, including SNCA (α-synuclein), LRRK2 (leucine-rich repeat kinase 2), Parkin (PARK2), PINK1 (PTEN-induced kinase 1), and GBA (glucocerebrosidase). Mutations or variations in these genes can increase the risk of developing Parkinson's disease.