SNCA and Parkinson disease: To this end, the prospective Parkinson Progression Marker’s Initiative (PPMI) has been expanded to include prodromal PD cohorts including subjects with hyposmia or RBD who meet a threshold for DAT deficit as well as genetic mutations in LRRK2, GBA, or SNCA (https://www.ppmi-info.org/study-design; last accessed 12/2021).