Among the proteins changed in CFS in respect to the healthy subject, we found two proteins which belong to the cysteine proteinase inhibitors family: cystatin C and B. Cystatins function as tight-binding inhibitors of cathepsins, which are cysteine proteinases involved in a number of important cellular processes including inflammation [50]. The gene discussed is CST3; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.