A Rare Type of Myeloma: A Case of Monoclonal IgD-Lambda.

An immunoglobulin D-multiple myeloma (IgD-MM) case represents a rare subtype of MM that is often observed in male patients under 65 years of age with an advanced stage at the time of diagnosis. It exhibits an aggressive course and is associated with a short survival period. In IgD-MM, an increase in lambda light chain proteins is expected. Given that IgD and IgE heavy chains are not routinely assessed in standard serum and serum immunofixation electrophoresis (IFE) analyses in MM patients, such cases may be misclassified and monitored as light chain myeloma. Therefore, distinguishing IgD or IgE myeloma from light chain myeloma represents a critical differential diagnosis. This case highlights the necessity of including IgD and IgE in diagnostic evaluations to prevent misclassification as light chain myeloma.