GBA1 and Parkinson disease: α-Syn SAA: α-synuclein seed amplification assays; CSF: cerebrospinal fluid; PD: Parkinson’s disease; IHC: immunohistochemistry; DAT-SPECT: dopamine transporter single-photon emission CT; PET: positron-emission tomography; GFAP: glial fibrillary acidic protein; GBA: glucocerebrosidase; LRRK2: leucine-rich repeat kinase 2; PRS: polygenic risk score; LP: lumbar puncture