Shimizu M, et al. – The clinical significance of soluble tumor necrosis factor receptor (sTNFR) II/I ratio as an indicator of the diagnosis of macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (s–JIA), was examined. As MAS developed, the sTNFRII/I ratio profoundly increased and had an association with disease activity. As compared with Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis (EBVHLH) patients, serum IL–18 levels were significantly elevated in MAS patients. For the diagnosis of MAS and the differentiation between MAS and EBVHLH, the monitoring of serum IL–18 and sTNFRII/I appeared to be useful