In accordance with a recent report stating that severe ME/CFS patients differover time from moderate ME/CFS patients and express significant immune abnormalities [17], our results indicate that the simultaneous monitoring of the muscle function, redox response, and CD26-expression could contribute, together with the health status scales, to identifying ME/CFS and to assessing its severity. The gene discussed is DPP4; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.