hemophagocytosis hemophagocytosis hemophagocytosis is phagocytosis by histiocytes of erythrocytes, leukocytes, platelets, and their precursors in bone marrow and other tissues. micrograph showing hemophagocytosis in the spleen. h&e stain. it is part of the presentation of hemophagocytic lymphohistiocytosis and macrophage activation syndrome. it has also been seen at autopsy of people who died of covid-19.