An Infant with Prolonged Fever, Splenomegaly, and Rash

Hemophagocytic lymphohistiocytosis and the related disease macrophage activation syndrome are dangerous disorders of immune hyperactivation affecting multiple organ systems with a high mortality rate. They often present with prolonged fever, hepatosplenomegaly, and a range of lab abnormalities. Triggers include infections, malignancies, immunodeficiencies, immunosuppression, and rheumatologic disorders. Treatment often involves chemotherapy.