PSAP and Parkinson disease: Based on aforementioned inconsistent results regarding the effect of PSAP intronic variants on the risk of PD, this study aims to clarify the role of PSAP variants in different subgroups of PD among Taiwanese population by enrolling patients with early-onset PD (EOPD), who have the onset age of PD before 50 years old, and patients with familial PD (FPD), who have a family history of PD, patients with sporadic PD (SPD), who have no family history and have disease onset older than 50 years of age, and health controls (HC).