Chapter

Paraproteins and the kidney

Robin G. Woolfson

in Cancer and the Kidney

Second edition

Published on behalf of Oxford University Press

Published in print November 2010 | ISBN: 9780199580194
Published online November 2012 | e-ISBN: 9780191753404 | DOI: http://dx.doi.org/10.1093/med/9780199580194.003.0004

Series: Oxford Clinical Nephrology Series

Paraproteins and the kidney

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Plasma cells are mature B lymphocytes which produce heavy and light chains and these assemble in tetramers to form different classes of immunoglobulins (IgG, IgA, IgM, IgE, IgD). Each immunoglobulin comprises two heavy chains and two light chains, either kappa (κ) or lambda (λ), based on the amino acid sequence in the constant portion of the polypeptide chain. In a plasma cell dyscrasia or malignancy, an autonomous clone produce a monoclonal paraprotein (M-band) which can be a whole immunoglobulin or a light chain or a heavy chain. Filtered light chains may damage glomerular mesangial cells or the epithelial cells which line the proximal or distal tubules.

Fifty-two percent of plasma cell tumors produce IgG, compared with IgA in 21%, IgM (Waldenstrom’s) in 12% and light chains alone in 11%. Rarely, plasma cell tumors are non-secretory and the diagnosis is suggested by the presence of an immune-paresis due to the suppression of the normal plasma cell population. Although usually restricted to the bone marrow, extra-medullary deposits (plasmacytomas) and plasma cell leukemias can occur.

The clinical significance of an M-band is protean. In monoclonal gammopathy of unknown significance (MGUS), which comprises the largest clinical group, the M-band is not associated with any other clinical features or identifiable plasma cell dyscrasia. At the other end of the spectrum, multiple myeloma is due to a malignant plasma cell tumor with clinical presentation dependent on the tumor load present in bone marrow, plasma levels of paraprotein, and metabolic consequences. In intermediate conditions, it may be possible to identify a plasma cell dyscrasia but the clinical presentation is determined by the biochemical properties of the paraprotein and the nature and distribution of deposits within the kidney and elsewhere. Paraprotein disease should be considered in any patient who presents with microscopic hematuria, proteinuria, nephrotic syndrome and kidney disease, either acute or chronic.

Chapter.  14522 words.  Illustrated.

Subjects: Nephrology

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