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.