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Immunoelectrophoresis of urine proteins
Last reviewed: 05.07.2025
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Paraproteins are normally absent in urine.
In immunoglobulinopathy, an increase in the concentration of serum proteins, especially macroglobulins, or Ig, combined into immune complexes with blood clotting factors or other antigens, causes an increase in blood viscosity, which in turn leads to circulatory disorders in small vessels and damage to their walls by immune complexes. In these cases, the kidneys are primarily affected, which is manifested by proteinuria. Characteristics of proteinuria are 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 total urine protein is noted in almost 90% of such patients. Immunoelectrophoresis of urine proteins allows us to identify pathological PIgA, PIgM, PIgG, H-chains, and Bence-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 are also found in 50-60% of cases of IgG and IgA paraproteinemia and in almost all patients with D-myeloma. In Waldenstrom's macroglobulinemia, Bence-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 Bence-Jones protein in the urine has special diagnostic and prognostic value. This protein, penetrating the tubules, damages their epithelium and infiltrates the interstitium, resulting in sclerosis of the renal stroma, which leads to the development of renal failure - the most common cause of death in myeloma. When the Bence-Jones protein is detected, it must be typed: the nephrotoxic effect of the λ type protein is significantly higher than that of the κ type protein.
The excretion of Bence-Jones protein in urine usually indicates the presence of a tumor process, since it is not formed in reactive paraproteinemias. Therefore, early detection of Bence-Jones protein in urine, even in trace amounts, is necessary for early diagnosis of multiple myeloma. It should be remembered that the excretion of Bence-Jones protein in urine is observed in almost 50% of cases of chronic leukemia.
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