Mutations in some genes—e.g., α-Synuclein (SNCA), Parkin 2 (PARK2), PTEN-induced putative kinase 1 (PINK1), PARK7, Leucine-rich repeat kinase 2 (LRRK2), Bone narrow stromal cell antigen 1 (BST1), Microtubule-associated protein tau (MAPT)—might be causative in familial forms of PD whereas diverse genetic defects in other loci might represent susceptibility loci associated with sporadic PD without family history [28,34,35,36,37,38,39]. Here, LRRK2 is linked to Parkinson disease.