Characteristic elevation of soluble TNF receptor II : I ratio in macrophage activation syndrome with systemic juvenile idiopathic arthritis.

Summary: To investigate the clinical significance of soluble tumour necrosis factor receptor (sTNF‐R) II/I ratio as an indicator of the diagnosis of macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (s‐JIA), we measured the serum sTNF‐RI and II levels in 117 patients with s‐JIA, including 29 patients with MAS, 15 with Epstein–Barr virus‐induced haemophagocytic lymphohistiocytosis (EBV‐HLH), 15 with Kawasaki disease (KD) and 28 healthy controls (HCs). We determined their correlation with measurements of disease activity and severity. Furthermore, we measured serum interleukin (IL)‐18 levels in patients with EBV‐HLH and compared these in levels in patients with MAS. The sTNF‐RII/I ratio was elevated significantly in MAS and EBV‐HLH patients compared with those in the acute phase of s‐JIA and KD patients, whereas there were no significant differences between HCs and those in the acute phase of s‐JIA. The sTNF‐RII/I ratio increased profoundly as MAS developed and correlated positively with disease activity. Serum IL‐18 levels were elevated significantly in MAS patients compared with EBV‐HLH patients. The monitoring of serum IL‐18 and sTNF‐RII/I might be useful for the diagnosis of MAS and the differentiation between MAS and EBV‐HLH. [ABSTRACT FROM AUTHOR]