GBA1 and Parkinson disease: To address these questions, we investigated 5 CSF d18:1 sphingolipid species (Cer (d18:1/18:0), GlcCer (d18:1/18:0), SphM (d18:1/18:0), GlcSph (d18:1) and GalSph (d18:1)) in a multicenter cohort with 152 PD and 37 DLB participants with and without heterozygous GBA1 variants.