Acute nonlymphocytic leukemia complicated by severe cytophagocytosis of formed blood elements by nonmalignant histiocytes: Cause of significant clinical morbidity

A 52‐year‐old female presented with Philadelphia chromosome‐positive acute nonlymphocytic leukemia and a morphologically benign‐appearing histiocytosis with intramedullary cytophagocytosis of formed blood elements. No cause of the reactive histiocytosis could be found. Despite initial successful therapy of the acute nonlymphocytic leukemia with induction of a cytological remission, pancytopenia with marked cytophagocytosis persisted. Therapy aimed at reducing the degree of cytophagocytosis by the histiocytes, in the form of vinblastine‐treated platelets and, subsequently, prednisone, was instituted. There was no significant clinical response to either therapeutic maneuver. Cytophagocytosis persisted until leukemic relapse and death ensued.