Macrophage activation syndrome in a patient with systemic-onset juvenile idiopathic arthritis initially treated for atypical Kawasaki disease

Abstract

Systemic-onset juvenile idiopathic arthritis (SoJIA) is the most common rheumatic disorder in children and its presentation can mimic atypical Kawasaki disease. The diagnosis of SoJIA is often challenging and children are often diagnosed and treated for Kawasaki disease ini- tially, especially after an unremitting fever lasting for sev- eral days. This fact can delay the treatment of SoJIA as in- correct treatment with intravenous immunoglobulins (IVIG) is being given and this may probably lead to a worse out- come in those individuals. This is a case of a 12-month-old infant who was initially treated for atypical Kawasaki in- stead of a SoJIA presenting with a macrophage activating syndrome (MAS). We also present a review of the litera- ture that supports the diagnosis of SoJIA presenting with MAS.