Hemophagocytic Lymphohistiocytosis: A Dangerous Intruder in Pediatric Acute Lymphoblastic Leukemia.

Hemophagocytic lymphohistiocytosis (HLH) is a condition caused by a pathologic immune activation, which is responsible for its signs and symptoms. It may also appear as a secondary process caused by malignancy. Developing HLH during treatment for acute lymphoblastic leukemia (ALL) is extremely uncommon, but underdiagnosis may be fatal. Two patients with ALL on chemotherapy maintenance treatment who developed HLH triggered by infection are presented here. We emphasize the importance of being aware of this condition when a patient with ALL in complete remission presents with unexplained hepatomegaly, cytopenia, and fever. Early diagnosis and treatment may be lifesaving.