Hemophagocytic lymphohistiocytosis associated with influenza A (H1N1) infection in a patient with chronic lymphocytic leukemia: an autopsy case report and review of the literature.

H1N1 influenza A virus can trigger fatal hemophagocytic lymphohistiocytosis in immunocompromised patients and in immunocompetent hosts, usually children. We present a case of a 50-year-old man with low-burden chronic lymphocytic leukemia who had sudden reactivation of his leukemia triggered by influenza A (H1N1) infection with hemophagocytic lymphohistiocytosis during the 2009 H1N1 pandemic. His rapid course was complicated by acute respiratory distress syndrome with diffuse alveolar damage, a 6-fold rise in lymphocyte count, disseminated intravascular coagulation, and, ultimately, cardiac arrest. Major findings at autopsy included: bilateral H1N1 pneumonitis with diffuse alveolar damage, intra-alveolar pulmonary hemorrhage, pulmonary microthromboemboli, pulmonary hemorrhagic infarction, hemophagocytic lymphohistiocytosis in multiple locations, and diffuse chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis is a serious and often fatal condition, which may be primary or secondary. It may be associated with high-grade lymphoproliferative malignancies, especially in patients with therapy-related leukocytopenia, but only rarely is it seen in uncomplicated chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis may be triggered by a variety of infections (viral, fungal, bacterial and parasitic), but H1N1 influenza A-associated hemophagocytic lymphohistiocytosis is often rapidly fatal, especially in children. This adult patient's clinical presentation with low tumor burden and leukocytosis is thus unique. We review the recently published autopsy findings in fatal influenza A (H1N1) infection and the association with resultant secondary hemophagocytic lymphohistiocytosis. Published by Elsevier Inc.