RESUMEN
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 initially, especially after an unremitting fever lasting for several days. This fact can delay the treatment of SoJIA as incorrect treatment with intravenous immunoglobulins [IVIG] is being given and this may probably lead to a worse outcome in those individuals. This is a case of a 12-month-old infant who was initially treated for atypical Kawasaki instead of a SoJIA presenting with a macrophage activating syndrome [MAS]. We also present a review of the literature that supports the diagnosis of SoJIA presenting with MAS