Phagocytic multiple myeloma with disseminated intravascular coagulation.

We describe an atypical case of IgG lambda multiple myeloma in a 28-year-old patient. He developed multiple cutaneous plasmacytomas, and the terminal event, leukemic conversion by phagocytic plasma cells and disseminated intravascular coagulation. Secretion of monoclonal immunoglobulin (IgG lambda) from myeloma cells was demonstrated by plaque-forming cell assay. Electron microscopy showed myeloma cells with well-developed rough endoplasmic reticulum and erythroid cells or platelets in intracytoplasmic vacuoles.