SNCA and Parkinson disease: Therefore, this review will summarize the characteristics, clinical phenotypes, especially the NMS of monogenic PD patients bearing mutations in various PD-related genes including SNCA, the leucine-rich repeat kinase 2 (LRRK2), vacuolar protein sorting 35 (VPS35), Parkin, PTEN-induced putative kinase 1 (PINK1), DJ-1 and glucocerebrosidase (GBA).