MAPT and Parkinson disease: This cross‐sectional, observational study examined the levels of α‐syn across multiple biofluid matrices (ie, CSF, saliva, and plasma) and multiple CSF neurodegenerative biomarkers (ie, α‐syn, Aβ1‐42, t‐tau, and p‐tau) in a large sample of “typical,” moderate‐advanced PD and matched healthy control participants.