Whereas pleural effusions in multiple myeloma (MM) due to benign causes, including heart failure, renal impairment, and hypoalbuminemia, occur in about 6% of all patients, myelomatous pleural effusion (MPE) is a rarity. MPE indicates an aggressive course of MM, with an associated median survival time of approximately 4 months. Thus, prompt and appropriate workup of pleural effusions in MM is imperative. In addition to detection of atypical plasma cells in the pleural fluid and histologic confirmation of MPE, identification of a monoclonal protein in the pleural effusion is essential. Protein electrophoresis is often used. As in the case described by Oudart et al., however, light chain MM may represent a diagnostic obstacle, because only about 50% of cases exhibit a monoclonal band after serum protein electrophoresis, and even immunofixation of serum may not demonstrate a monoclonal band in all patients with light chain MM. In the reported case, immunofixation analysis and quantification of free light chains in the pleural effusion demonstrated the presence of monoclonal free light chains. Quantification of free light chains in a pleural effusion is a novel approach, and a higher concentration of free light chains in the pleural effusion than in the serum indicated local production in this case. With a median survival time of about 4 months in MPE patients, neither patients nor physicians have much time to obtain a proper diagnosis and to start adequate therapy. In such cases, the most sensitive diagnostic methods have to be used. Today, the most sensitive routine tests for detecting monoclonal components in serum are a combination of protein electrophoresis, immunofixation, and free light chain quantification. This is most likely also true for the detection of monoclonal proteins in pleural effusions, and these methods should therefore also be used to uncover the origin of pleural effusions associated with MM.
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Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.
- Received for publication April 15, 2011.
- Accepted for publication April 18, 2011.
- © 2012 The American Association for Clinical Chemistry