Macrophage activation syndrome in a patient with systemic onset of the juvenile idiopathic arthritis.

Systemic onset juvenile idiopathic arthritis (sJIA) is defined as arthritis affecting one or more joint usually in the juvenile age group (< 16 years of age) with or preceded by fever of at least 2 weeks duration that is documented to be daily ("quotidian") for at least 3 days which may be associated with evanescent (non-fixed) erythematous rash or generalized lymph node enlargement or hepatomegaly/splenomegaly/both or serositis. Macrophage activation syndrome (MAS) is a life-threatening complication of sJIA marked by sudden onset of non-remitting high fever, profound depression in all three blood cell lines (i.e. leukopenia, anemia, and thrombocytopenia), hepatosplenomegaly, lymphadenopathy, and elevated serum liver enzyme levels. In children with systemic juvenile idiopathic arthritis, the clinical picture may mimic sepsis or an exacerbation of the underlying disease. We report a case of a 16-year-old female patient presenting with high grade fever with joint pains and generalized weakness which proved to be systemic onset juvenile idiopathic arthritis with macrophage activation syndrome after ruling out all other differential diagnoses and responded well to intravenous steroids.