GBA1 and Parkinson disease: Using the Parkinson’s Progression Markers Initiative (PPMI) cohort (n = 455; 303 PD patients, 152 controls), we quantified plasma levels of these metabolites by quantitative LC-MS/MS with batch correction, examining sporadic PD and genetically defined subgroups (LRRK2-PD [PDL], GBA1-PD [PDG], dual-mutation PD [PDGL], and prodromal equivalents).