S100B and myalgic encephalomeyelitis/chronic fatigue syndrome: Therefore, it is essential to examine the possible relationship between chronic fatigue syndrome (CFS) and affective symptoms associated with long COVID, as well as various metabolic or immune-inflammatory biomarkers, including prostaglandin E2 (PGE2), insulin-like growth factor 1 (IGF-1), galanin (GAL) and its receptor type 1 (GALR1), plasminogen activator inhibitor (PAI)1, and neuronal damage indicators such as S100 calcium-binding protein B (S100B) and neuron-specific enolase (NSE).