Our key findings included (1) increased concentrations of CRP and cytokines IL-1β, TNF-α, IL-6, and Il-4 among both MSA and PSP patients compared to PD patients, but not compared to SCs; (2) except for IL-4, no significant differences between PD and SCs; and (3) the best diagnostic discrimination between PD and MSA, evaluated by ROC curves, was found with a combination of analytes. This evidence concerns the gene IL6 and Parkinson disease.