Macrophage Activation Syndrome as the First Presentation of Juvenile Idiopathic Arthritis

Macrophage activation syndrome (mas) is a rare feature of rheumatic disorders in children and adolescence and its presentation as the first symptom of rheumatic disorders is very infrequent. a 9-year-old girl, in whom mas developed, was admitted to our hospital in tehran, iran. she suffered from high grade fever and rash followed by multiple joint swelling months afterwards. bone marrow aspiration and biopsy showed normocellular marrow with a cellularity of 90%. benign-looking macrophages were remarkably increased; many of them showed hemophagocytic features. according to the presentation of long-standing fever and observation of “hemophagocytic macrophage” in bone marrow, mas was diagnosed for the patient. additionally, due to recurrent joint swelling in following months, she was diagnosed to be affected by “juvenile idiopathic arhtritis” complicated by mas. mas is a rare complication of rheumatic disorders which should be considered as the first presentation of rheumatic disorders in children specifically in those presenting with high fever, hepatosplenomegaly, lymphadenopathy and severe cytopenia.