Methods: We retrospectively analyzed our patients diagnosed with SoJIA between 1996-2015. Clinical features and laboratory parameters of patients who were diagnosed with MAS are reassessed according to 2016 criteria for MAS in SoJIA.

Results: 27 patients (32.1%, 13 boys and 14 girls) out of the 84 patients diagnosed with SoJIA, developed MAS. 7 patients had recurrent MAS episodes. Mean age of diagnosis for SoJIA was 5.8 ± 4.5 years and for the first MAS episode was 6.7 ± 5.2 years. 20 patients (22.9%) developed MAS at presentation of SoJIA while 7 patients developed it during the course of SoJIA. Among these 7, two patients were off treatment and the remaining patients were on biologic disease modifiying anti-rheumatic drugs (DMARDs) including infliximab, etanercept, anakinra, canakinumab and tocilizumab, in combination with classic DMARDs, except for one patient treated only with non-biologic agents. 14 patients fulfilled the 2016 criteria of MAS for SoJIA. Two patients did not have fever but met the lab criteria. Ferritin levels were not high enough in two patients. 11 patients had thrombocytopenia, 22 patients had increased AST, 9 had increased triglyceride and 10 patients had hypofibrinogenemia. No death occurred during the course of MAS.

Conclusion: Even if the criteria are not met, a high index of suspicion for MAS in SoJIA may be lifesaving. In addition to recently developed MAS criteria for SoJIA, following the trend of laboratory values can help to recognize a “developing MAS” and to treat accordingly early in the course.