Serum phosphorylated tau 217 in GBA1 variant carriers with and without Parkinson disease.

It is unclear whether Alzheimer disease pathology drives cognitive decline in Parkinson disease (PD) patients carrying GBA1 variants. We evaluated levels of serum phosphorylated tau 217 (p-tau217) in samples from 29 GBA1-PD, 32 idiopathic PD, 20 non-manifesting GBA1 variant carriers (GBA1-NMC) and 31 healthy controls. No differences were detected between PD groups. GBA1-NMCs showed higher levels than healthy controls, which correlated to worse cognition and subthreshold parkinsonism. Serum p-tau217 is not a marker of cognitive decline in GBA1-PD. Whether p-tau217 levels in GBA1-NMCs can predict conversion to PD or are a marker of cognitive decline, irrespective of PD, remains unknown.