Cytomegalovirus-associated hemophagocytic lymphohistiocytosis in a patient with myasthenia gravis treated with azathioprine.

A 47-year-old woman with myasthenia gravis treated with azathioprine, prednisone, and plasmapheresis was admitted for respiratory failure following 2 weeks of fever with splenomegaly, jaundice, coagulopathy, and pancytopenia (white blood cells, 1.1 3 10/L with 64% neutrophils; hemoglobin, 9.5 g/dL; platelets, 79 3 10/L) but no substantial schistocytosis. Triglyceride (330 mg/dL) and ferritin (7562 ng/mL) levels were elevated; fibrinogen level was decreased (52 mg/dL). Soluble CD25 level was markedly elevated (17 092 U/mL), and natural killer cell activity was absent. Plasma was positive for cytomegalovirus (CMV) DNA. Bone marrow examination revealed prominent histiocytic hyperplasia with numerous hemophagocytes (panels A-C). Rare large cells with CMV cytopathic effects (panel D) were also present (confirmed by immunohistochemical staining; panel E). A diagnosis of hemophagocytic lymphohistiocytosis (HLH) accompanied by CMV infection was rendered.