To identify clinical and laboratory predictors for early macrophage activation syndrome (MAS) associated with systemic juvenile idiopathic arthritis (sJIA).

This is a retrospective cohort study of 149 patients with sJIA, of whom 27 had 31 episodes of MAS. We evaluated the clinical and laboratory features of patients with sJIA and MAS and compared them with those without MAS. We focused our analysis on the overall process of MAS development, especially MAS onset.

As shown in previous studies, we found a high percentage of fever, absence of arthritis, and central nervous system dysfunction at MAS onset in our study cohort. We also found that 35% of patients with MAS had hypotension although not shock, and 22.6% of patients with MAS had gastrointestinal involvement at MAS onset. Compared with patients with MAS without hypotension, patients with MAS and hypotension had greater rates of admission to the intensive care unit; presented with more arthritis, serositis, pneumonia, and gastrointestinal involvement; and had greater white blood cell and absolute neutrophil counts and serum bilirubin levels and lower serum total protein. We confirmed laboratory markers such as platelet counts, lactate dehydrogenase, and aspartate aminotransferase can help to identify early MAS and that ferritin/erythrocyte sedimentation rate ratio of approximately 20.0 had a high diagnostic sensitivity and specificity for MAS. In addition, we discovered that the combination of interferon-γ >17.1 pg/mL and interleukin-10 >7.8 pg/mL appeared to be a good cytokine pattern for the recognition of MAS onset.

Sudden hypotension, elevated ferritin/erythrocyte sedimentation rate ratio, and the cytokine pattern of significantly increased interferon-γ and interleukin-10 levels are important markers for early identification of MAS in addition to the traditional characteristics of sJIA-associated MAS.