Genetic mutations cause familial forms of PD, including α-synuclein (SNCA), parkin (PRKN), leucine-rich repeat kinase-2 (LRRK2), and PTEN-induced putative kinase 1 (PINK1), which all individually result in aberrant α-synuclein activity and its subsequent aggregation [23,24,25]. This evidence concerns the gene LRRK2 and Parkinson disease.