Case of systemic-onset juvenile idiopathic arthritis complicated with sepsis --usefulness of cytokine profile for the differentiation between macrophage activation syndrome and sepsis.

The differential diagnosis of macrophage activation syndrome (MAS) and sepsis must be considered in the clinical course of systemic-onset juvenile idiopathic arthritis (s-JIA) with sudden onset of high-grade fever and abnormal laboratory findings, including leukocytopenia, thrombocytopenia, and coagulopathy. In this report, we describe the case of a 17-month-old girl diagnosed with s-JIA complicated with sepsis. Her serum interleukin (IL)-18 level was significantly elevated throughout the clinical course. Furthermore, compared to other MAS patients, she showed a significantly elevated serum IL-6 level and procalcitonin in sepsis. Therefore, our results suggest that a patient's cytokine profile may be a useful indicator of disease activity and may thus help in the differential diagnosis of sepsis and MAS in s-JIA.