In an attempt to identify biomarkers for Parkinson disease (PD), researchers have assessed known plasma markers of neuronal function, inflammation and cardiovascular risk in 109 people with PD and 96 healthy matched controls. The results revealed 25 proteins that were differentially expressed in PD, which were validated in an independent cohort. A number of markers correlated with cognitive decline and motor deterioration at follow-up, demonstrating their utility for monitoring disease progression. The findings also offer insight into pathological pathways of PD and identify potential therapeutic targets.