[IgM myeloma]

Abstract

The authors report the case of a 62 year old woman in whom bony pain led to the discovery of lacunar osteolytic appearances, in particular in the skull, abnormal medullary plasmacytosis and serum monoclonal immunoglobulin with Bence-Jones proteinuria. The case was unusual as the immunoglobulin observed was an IgM. This finding led the authors to a critical revision of the distinctive characteristics of multiple myeloma and Waldenström's macro-globulinemia, emphasizing the distinguishing value of the cytological criterion. The authors recall the various neoplastic proliferations of the B lymphocytes at the various stages of their maturation and emphasize the predominance of monoclonal IgM during proliferations affecting the early stages of maturation of the B lymphocytes and the rareness of these IgM during plasma cell neoplasms.