CHRM1 and myalgic encephalomeyelitis/chronic fatigue syndrome: While an enzyme-linked immunosorbent assay (ELISA) analysis has failed to identify GPCR aAB in the CSF of ME/CFS patients (Bynke et al., 2020), the presence of serum aAB against the muscarinic acetylcholine receptor M1 (M1R) correlated with impeded receptor binding in a brain PET study, suggesting leakage of aAB across the BBB (Yamamoto et al., 2012).