Serum phosphorylated tau 217 in <i>GBA1</i> variant carriers with and without Parkinson disease

It is unclear whether Alzheimer disease pathology drives cognitive decline in Parkinson disease (PD) patients carrying <i>GBA1</i> variants. We evaluated levels of serum phosphorylated tau 217 (p-tau217) in samples from 29 <i>GBA1</i>-PD, 32 idiopathic PD, 20 non-manifesting <i>GBA1</i> variant carriers (<i>GBA1</i>-NMC) and 31 healthy controls. No differences were detected between PD groups. <i>GBA1</i>-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 <i>GBA1</i>-PD. Whether p-tau217 levels in <i>GBA1</i>-NMCs can predict conversion to PD or are a marker of cognitive decline, irrespective of PD, remains unknown.