Patient selection:
(1) clinical suspicion of plasma cell disorder
(2) serum and urine protein immunoglobulin electrophoresis are negative for monoclonal protein
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Clinical Finding
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Workup
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lytic bone lesion
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Perform a directed biopsy of the lytic area.
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hypogammaglobulinemia of IgG, IgM, IgA and/or IgD
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Perform a free light chain analysis on serum.
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High levels of free light chains may go undetected on immunfixation, probably because of variable polymerization of the light chains. The serum free light chain test is much more sensitive.
If the free light chain analysis on serum shows a clonal abnormality, then perform a bone marrow aspirate and core biopsy with:
(1) cytogenetics
(2) immunohistochemistry for CD79a, CD138, kappa light chains, lambda light chains.
Repeat testing after several months may be indicated if initial tests are negative and the clinical suspicion is high.
A patient with clonality on the serum free light chain assay should NOT be classified as nonsecretory. The term nonsecretory should be reserved for myeloma with all serum and urine tests negative for clonal proteins.
Differential diagnosis of hypogammaglobulinemia:
(1) nephrotic syndrome
(2) protein losing enteropathy
(3) primary immunodeficiency
(4) immunosuppression
(5) CLL or other hematologic malignancy
