Prolonged Fever in a Pediatric Patient: A Case of Systemic Juvenile Idiopathic Arthritis (sJIA) Complicated by Macrophage Activation Syndrome (MAS).

A prolonged fever in a child can be due to a range of causes including infectious, autoimmune, malignant, or genetic in etiology. In our report, we present the case of a previously healthy three-year-old female diagnosed with macrophage activation syndrome (MAS) due to complications of systemic juvenile arthritis (sJIA). MAS is considered a secondary subtype of hemophagocytic lymphohistiocytosis (HLH), a rare and life-threatening group of syndromes characterized by overstimulation of the immune system leading to systemic inflammation.