Busser et al. have shared an unusual case featuring a broad, prominent increase in the β region of a urine protein electrophoresis result. The immunofixation electrophoresis (IFE) result identifying the band in serum and urine as containing only γ chains with no corresponding light chain secured the diagnosis of γ–heavy chain disease.
The serum protein electrophoresis had been performed by capillary electrophoresis, a technique in which radiocontrast dyes and antibiotics can create spikes that mimic an M protein (1,–,5). Such spikes are typically quite discrete, however. Hemoglobin and fibrinogen are other common M protein mimics, but they have characteristic migrations that clinical laboratories usually recognize (6).
Some M proteins that migrate in the β region of serum can be quite subtle and easily missed. Narayan et al. reported that in electrophoresis systems that produce crisp resolution of the β1- and β2-globulins, an increase in either of these fractions not explained by an obvious process, such as β–γ bridging, deserves an IFE evaluation (7). These investigators reported that of 36 samples with such an increase, 12 had an M protein by IFE. Similarly, Katzmann et al. found M proteins when they reflexed to IFE serum samples that had the following suspicious findings: “fuzzy” bands (54% M proteins), β regions of 1.6–1.9 g/dL (16–19 g/L) (10% M proteins), and hypogammaglobulinemia (12% M proteins) (6).
An unusual phenomenon, “phantom light chain,” rarely accounts for an apparent lack of a light chain in some cases of myeloma. This term, coined by Cejka and Kithier and originally described in a case of IgD λ myeloma (8), has also been reported in a case of IgA λ myeloma (9). The apparent lack of light chains by IFE may be due to heavy chains cloaking light chain determinants; however, by using other antisera, or a stronger concentration of the antisera, one can demonstrate the light chains (9).
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.
- Received for publication February 16, 2010.
- Accepted for publication February 24, 2011.
- © 2011 The American Association for Clinical Chemistry