L1CAM and Parkinson disease: Specifically, α-synuclein content in L1CAM-positive exosomes is similarly elevated (data shown as mean±SD) in RBD (26.69±12.82 pg/mL), motor PD (27.44±18.82 pg/mL) and PD with dementia (PDD 26.76±17.25 pg/mL) when compared with healthy subjects (HC, 12.71±5.93 pg/mL).