Acute myelomonocytic leukemia associated with paraproteinemia

A 49-year-old white woman with refractory anemia subsequently developed acute myelomonocytic leukemia with paraproteinemia 12 months later. The paraprotein was characterized as immunoglobulin G, type kappa, and the Bence Jones protein as free kappa chains. Further studies, including electron microscopy, cytochemistry, and immunofluorescence provided evidence for synthesis of the paraprotein, both in vivo and vitro, by the myelomonocytic leukemic cells.