Hemophagocytic lymphohistiocytosis during maintenance treatment of precursor B-cell acute lymphoblastic leukemia

Hemophagocytic lymphohistiocytosis (HLH) is a rare but occasionally life-threatening disorder. HLH is characterized by hypercytokinemia induced by activated T-cells and macrophages, resulting in hemophagocytosis in bone marrow and other reticuloendothelial systems. Prompt diagnosis and the implementation of appropriate therapy are mandatory; otherwise this uncontrolled hypersecretion of inflammatory cytokines leads to the hyperactivation of macrophages, hypercoagulability and bone marrow suppression, resulting in multiple-organ failure [1]. The development of HLH is thought to be quite rare in patients with acute lymphoblastic leukemia (ALL) [2]. In a Japanese nationwide survey, among 567 patients diagnosed with HLH over the last 5 years it was clarified that only 3 patients with ALL (0.5%) and 9 patients with AML (1.5%) developed HLH [3]. Herein, we report a case of HLH associated with an infection that was caused by an unidentified pathogen during the maintenance phase of precursor B-cell ALL; this patient was successfully treated with immunochemotherapy including etoposide. A 2-year-old boy was admitted to our hospital with a complaint of fever. He had previously been healthy, and there was no family history of particular note. Bone marrow aspiration showed proliferation of lymphoid cells which