LRRK2 and Parkinson disease: Most commonly, PD arises idiopathically, however familial forms of the disease can occur, most frequently due to inherited mutations in SNCA, LRRK2 (leucin-rich repeat kinase 2), PARK7 (parkinson protein 7), PINK1 (PTEN-induced kinase 1), or PRKN (parkin) genes.