Hemophagocytic, non-secretory multiple myeloma.

A 70-year-old woman presented with pancytopenia associated with plasma cell infiltration of her bone marrow. The plasma cells were often multinucleated and demonstrated phagocytosis of erythroid and granulocytic cells. Atypical immunophenotypic features included the expression of CD117 and CD13 and the lack of expression of CD56. Although kappa chains were demonstrable in the cytoplasm, no paraprotein was found in the serum or urine. Osteolytic lesions were absent. The pancytopenia of this unusual patient with non-secretory, hemophagocytic myeloma has improved on dexamethasone monotherapy, although her hemophagocytosis persists.