LRRK2 and Parkinson disease: Approximately 90 % of PD patients have no known cause (idiopathic), while the remaining 10 % have familial PD caused by mutations in specific genes like SNCA, PRKN/PARK2, PINK1, LRRK2, PARK7, DJ-1, GBA, UCH-L1, and MAPT/STH.