Plasmablastic light chain myeloma presenting as pancytopenia: An unusual presentation.

Light chain myeloma (LCM) is an unusual neoplasm accounting for about 1 8% of all plasma cell myelomas. It is characterized by the absence of a detectable M protein in the serum and urine protein electrophoresis, altered free light chain ratio, bone marrow plasmacytosis and related organ or tissue damage. We report a 60-year-old man with LCM presenting with pancytopenia. Urine Bence Jones proteins were negative and serum protein electrophoresis did not reveal an M-band. However, bone marrow biopsy showed plasmablastic morphology. Subsequent immunohistochemistry showed lambda restriction and cells positive for CD138 and IgM.