High urinary light chain proteins can be seen in physiologic conditions as well as in pathological conditions such as proliferative diseases of the immune system and renal diseases.
Immunoglobulin is composed of two identical light chains and two identical heavy chains. The light chains are small molecule proteins, which are freely passed through the glomerular basement membrane and then reabsorbed in the renal tubules and returned to the blood circulation.
1. Physiological conditions: such as strenuous exercise or exertion, cold, fever, mental stress, etc.
2. Pathologic conditions: including immunoproliferative systemic diseases, renal diseases and so on.
(1) Immunoproliferative system diseases: the body secretes a large amount of immunoglobulin, and the concentration of light chain in the blood is elevated, which can overflow from the urine when it exceeds the reabsorption threshold of the renal tubules, such as multiple myeloma.
(2) Renal diseases: under the exclusion of proliferative diseases of the immune system, it suggests that renal tubular reabsorption function is reduced, which can be used as a sign of renal tubular injury. Light chain protein can occasionally be detected in the urine of patients with pyelonephritis, chronic nephritis, renal cancer and nephrotic syndrome.
Excluding physiological factors, the doctor needs to make a comprehensive judgment based on the patient’s medical history, symptoms, physical examination and other auxiliary tests to determine the elevation of light chain protein in urine, and cannot rely on a single test indicator.