Systemic babesiosis. Another cause of the hemophagocytic syndrome.

Hemophagocytosis is a pathologic finding in a variety of infectious diseases associated with peripheral pancytopenia. In addition, hemophagocytosis is a prominent finding in malignant histiocytosis, a primary disorder of the monocyte-macrophage system. Systemic babesiosis is a rare parasitic disorder associated with intraerythrocytic parasites in the peripheral blood. There has been no description of the marrow findings in this disorder. A patient is described who had systemic babesiosis and prominent hemophagocytosis that disappeared after appropriate antiparasitic therapy. Systemic babesiosis should be considered in the differential diagnosis of hemophagocytosis.