Abstract
Protein electrophoresis (PEP) separates proteins based on mobility through support media such as agarose into five general regions: albumin, alpha-1, alpha-2, beta, and gamma. Monoclonal and polyclonal immunoglobulins typically migrate in the gamma or beta regions. Between April 1990 and July 2007 at Columbia University Medical Center, we identified and then retrospectively reviewed 15 patients with monoclonal proteins of alpha-2 mobility repeatedly on serum PEP (see figure). Immunofixation identified the paraprotein as IgA kappa in 7 patients, IgA lambda in 2, IgG lambda in 2, free kappa light chain in 4, free lambda light chain in 2, and one IgG lambda. In the urine, of the 14 patients who had PEP performed, 6 patients had serum concordant light chains (5 kappa and 1 lambda) also migrating in the alpha 2 region, however, for 5 other patients migration was either in the beta or gamma regions. Published case reports of monoclonal proteins with atypical mobility patterns are reviewed. The median age of our patients was 66 years and there were 9 males. 10 patients had multiple myeloma, 5 had monoclonal gammopathy of undetermined significance (MGUS), and 1 had lambda AL amyloidosis. This is the largest case series ever described of patients with monoclonal proteins migrating in alpha 2 region and illustrates the importance of immunofixation in screening patients for plasma cell dyscrasias. Possible explanations for this unusual migration pattern include protein complex formation with other plasma components, high carbohydrate content, or given the IgA predominance noted, properties of the IgA immunoglobulin such as polymerization.
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