This case describes the usefulness of measuring free light chains (FLCs) found in the pleural fluid to support the diagnosis of myelomatous pleural effusion. Serum FLC analysis has become an important tool for the diagnosis, prognosis, and response to therapy for such plasma cell dyscrasias as multiple myeloma (MM) and primary amyloid light chain amyloidosis. The FLC assay differs from previous methods of light chain detection by using polyclonal antibodies that bind to “hidden” epitopes present when the light chains are bound to the immunoglobulin heavy chain. Although there are some potential limitations of the FLC assay (1), it has become an important tool for the diagnosis and management of plasma cell disorders.
Patients with MM have a malignant plasma cell clonal population in the bone marrow and often present with problems relating to lytic bone lesions, anemia, renal insufficiency, and hypercalcemia. Extramedullary involvement of MM can occur in almost any tissue type but is rare at the time of diagnosis. It is more common in patients with relapsed and refractory disease. There are data suggesting that the incidence of extramedullary disease has increased in the era of novel chemotherapeutic agents being used for this disease, such as thalidomide, bortezomib, and lenalidomide (2).
It is not stated whether the patient in the current case was previously treated with chemotherapy and what agents might have been used, but given the clinical history it is likely that she has relapsed disease. Differentiating the cause of pleural effusions in patients with MM is essential for implementing the appropriate therapy. The diagnosis of a myelomatous pleural effusion can be difficult, especially in patients with light chain myeloma. The use of the FLC assay was essential for providing the diagnosis in this case and should be included in the diagnostic workup.
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: Upon manuscript submission, all authors completed the Disclosures of Potential Conflict of Interest form. Potential conflicts of interest:
Employment or Leadership: None declared.
Consultant or Advisory Role: None declared.
Stock Ownership: None declared.
Honoraria: K. Stockerl-Goldstein, Celgene speakers bureau and Millennium speakers bureau.
Research Funding: None declared.
Expert Testimony: None declared.
- Received for publication January 9, 2012.
- Accepted for publication January 13, 2012.
- © 2012 The American Association for Clinical Chemistry