SLC6A3 and Parkinson disease: We analyzed a total of 851 individuals without pathogenic variants in LRRK2, PINK1, PRKN, or SNCA, including 449 PD patients (87 EOPD, 354 LOPD, and 8 with unknown age at onset), 144 prodromal subjects, 63 SWEDD cases (clinically diagnosed with PD but exhibiting normal DAT SPECT imaging), and 195 healthy controls.