Polymerized IgA Monoclonal Gammopathy Simulating Biclonal Gammopathy: A Case Report

Serum protein electrophoresis (SPEP) typically reveals a single monoclonal (M) band in cases of monoclonal gammopathy (MG). Occasionally, two bands may appear, suggesting biclonal gammopathy. However, certain monoclonal immunoglobulins (Ig), particularly IgA, may exist in multiple polymerization states, mimicking biclonal patterns. We report the case of a patient with chronic renal failure referred for routine evaluation. SPEP revealed two monoclonal bands in the beta-2 and gamma-globulin regions, raising suspicion of biclonal gammopathy. Immunotyping (IT) identified both bands as IgA lambda, suggesting either biclonality or different polymerization states of the same monoclonal protein. To clarify, serum was treated with beta-mercaptoethanol. Post-reduction IT showed persistence of the beta-2-globulin band and disappearance of the gamma-globulin band, confirming a single IgA lambda monoclonal component with two distinct polymerization states. IgA MGs can exhibit atypical electrophoretic patterns due to variable polymerization, which may mimic biclonal patterns. In such scenarios, chemical reduction with beta-mercaptoethanol serves as a critical tool for accurate diagnosis.