A paraprotein is an immunoglobulin or immunoglobulin light-chain that is produced in excess by the clonal proliferation of plasma cells. Detection of paraproteins in the urine or blood is most often associated with benign MGUS (monoclonal gammopathy of undetermined significance), where they remain "silent", and multiple myeloma. An excess in the blood is known as paraproteinemia. Paraproteins form a narrow band, or 'spike' in protein electrophoresis as they are all exactly the same protein.
Paraproteins are also referred to as "M proteins," where the "M" stands for "monoclonal."
Monoclonal free light chains in the serum or urine are called Bence Jones proteins.
Paraproteins allowed the detailed study of immunoglobulins, which eventually led to the production of monoclonal antibodies in 1975.
Interpretation upon detection
Blood serum paraprotein levels of more than 30 g/L is diagnostic of multiple myeloma, according to the diagnostic criteria of the International Myeloma Working Group, which were updated in 2009. Detection of paraprotein in serum of less than 30 g/L is classified as monoclonal gammopathy of undetermined significance in cases where clonal plasma cells constitute less than 10% on bone marrow biopsy and there are no myeloma-related organ or tissue impairment.
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- Paraproteins at the US National Library of Medicine Medical Subject Headings (MeSH)
- Educational Resource for Paraproteins
- Paraprotein typing
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