Systemic juvenile idiopathic arthritis (SJIA) is currently classified as a subtype of juvenile idiopathic arthritis but with the addition of systemic inflammation often resulting in fever, rash and serositis. New research shows that the arthritic and systemic components of SJIA are related, but that the inflammatory pathways involved in SJIA are different from those in the more common polyarticular juvenile idiopathic arthritis (POLY).