Evaluation of Double M-Band on Serum Protein Electrophoresis Simulating Biclonal Gammopathy: A Case Report.

Multiple myeloma is characterized by the presence of M-protein (monoclonal) in blood or urine. These proteins are immunoglobulins which are produced by a clone of abnormally proliferating B-lymphocytes and/or plasma cells. To evaluate M-protein, serum protein electrophoresis (SPEP) is used where a single band, known as M-band is seen. This band is usually seen in the gamma globulin region. However, in rare entities like biclonal gammopathy, two M-bands appear simultaneously at different positions on SPEP which may be attributed to the clonal expansion of two different neoplastic cell lines. Here, we describe an atypical case of IgA-kappa multiple myeloma, where two M-bands (one in the beta region and one in the gamma globulin region) were found during SPEP. This simulated a picture of biclonal gammopathy. However the monoclonal nature of this M-protein was proved by performing immunofixation electrophoresis (IFE). Further, we put across images to explain how IFE helps in differentiating between apparent and true biclonality. © Association of Clinical Biochemists of India 2021.