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Immunoelectrophoresis of urine proteins
Last reviewed: 18.10.2021
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Paraproteins in the urine are normally absent.
In immunoglobulinopathy, an increase in the concentration of whey proteins, especially macroglobulins, or Ig, combined in immune complexes with clotting factors or other antigens, causes an increase in blood viscosity, which in turn leads to circulatory disturbances in small vessels and damage to their walls by immune complexes. In these cases, the kidneys primarily suffer, which is manifested by proteinuria. Characterization of proteinuria is necessary to clarify the nature of immunoglobulinopathies. One of the causes of proteinuria is the appearance of pathological proteins in the urine of patients with myeloma. An increased content of the total urine protein is noted in almost 90% of such patients. Immunoelectrophoresis of urine proteins allows to reveal pathological PIgA, PIgM, PIgG, H-chains, Bens-Jones protein. Approximately 15-20% of all cases of myeloma are represented by Bence-Jones myeloma, characterized by the formation of exclusively monoclonal light chains. Monoclonal light chains also show up in 50-60% of cases of IgG- and IgA-paraproteinemia and practically in all patients with D-myeloma. With Waldenström macroglobulinemia, the Bens-Jones protein is found in 60-70% of cases, but the total amount of protein in the urine does not exceed 200 mg / day. Identification of the Bence-Jones protein in the urine has a special diagnostic and prognostic significance. This protein, penetrating the tubules, damages their epithelium and infiltrates the interstitium, resulting in the sclerosis of the kidney stroma, which leads to the development of renal failure - the most common cause of death in myeloma. When a Bens-Jones protein is detected, its typing is necessary: the nephrotoxic effect of a protein of the λ type is much higher than the protein of the κ type.
Isolation of the Bence-Jones protein in the urine, as a rule, indicates the presence of a tumor process, since it does not form with reactive paraproteinemias. Therefore, early detection of the Bence-Jones protein in the urine, even in trace amounts, is necessary for the early diagnosis of multiple myeloma. It should be remembered that the secretion of the Bence-Jones protein in urine is observed in almost 50% of cases of chronic leukemia.
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