Immunoglobulin G kappa biclonal gammopathy associated with multiple myeloma, plasmacytoma and cast nephropathy

Biclonal gammopathies are characterized by simultaneous appearance of two different monoclonal proteins. Multiclonal gammopathies may be the result of a neoplastic transformation of a cell clone undergoing immunoglobulin (Ig) class switching or due to an independent neoplastic transformation event yielding proliferation of unrelated plasma cell clones. This in turn has implication on the disease manifestation, progression, prognosis and response to therapy. The prevalence of biclonal gammopathy is approximately 1% of all gammopathies and the most common combinations are IgG and IgA (33%), followed by IgM and IgG (24%). Multiple myeloma with biclonal gammopathy is very uncommon. The present case corresponds to an extremely rare occurrence of multiple myeloma with biclonal gammopathy revealing expression of two distinct monoclonal gammaglobulins both of IgG and kappa (κ) subtype in a 56-year-old diabetic man who presented with lower back pain and renal failure. To the best of our knowledge, only one case of IgG κ biclonal gammopathy associated with multiple myeloma have been reported in English literature. This case interestingly also had paraspinal plasmacytoma and cast nephropathy.