Development of a histiocytic medullary reticulosis-like syndrome during the course of acute lymphocytic leukemia.

A 54 year old woman presented with acute lymphocytic leukemia. Following an initial response to chemotherapy with vincristine and prednisone, progressive pancytopenia developed coincident with intense bone marrow infiltration by abnormal histiocytes. At autopsy two months later, no evidence of leukemia was found, but the bone marrow was replaced by abnormal histiocytes showing active erythrophagocytosis, consistent with histiocytic medullary reticulosis. Detailed morphologic, ultrastructural and histochemical studies performed throughout the course of the patient's illness served to confirm the transition from leukemia to histiocytosis. Four similar cases of acute lymphocytic leukemia terminating in histiocytic medullary reticulosis have been reported. This association may represent a distinct clinicopathologic syndrome.