S100B and Parkinson disease: Alongside elevated pro-inflammatory markers, fatigue in PD is also associated with increased levels of neuronal damage markers, including neuron-specific enolase (NSE), S100 calcium-binding protein B (S100B), phosphorylated tau217 (pTau217), and glial fibrillary acidic protein (GFAP), underscoring the interplay between peripheral immune-inflammatory activation and damage to glial projections and neurofilaments in its pathophysiology (41).