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Myeloma is a condition in which the plasma cells that normally make antibodies become cancerous, examining urine and serum of blood can make the diagnosis effective. The condition is monoclonal gammopathy, in which immune cells-plasma cells start making just one immunoglobulin, or antibody, instead of their usual vast array.
The different tests look in the serum or urine for signs of the abnormal antibody, and to see if the usual ratio is off for two types of a portion of the antibody, called light chains. If the multiple myeloma is associated with lambda light chain, there is about a 25 percent chance the problem will not be detected by the serum test for free light chains.
Serum free light chain assay is not enough in detecting lambda chain-associated lesion. Plasma cells are immune cells that live in bone marrow and produce immunoglobulins, antibodies that attach to and attack invaders. When the plasma cells go bad, they produce a single, dysfunctional immunoglobulin.
The Y-shaped immunoglobulins are comprised of pieces of protein called “heavy” and “light” chains. Light chains have two different types, kappa and lambda, which are distinctive in their amino acid sequence. Human make about twice as many kappa light chains, but cancer can affect both light chains.
In multiple myeloma, the relevant light chain production goes up but kappa goes up a lot more. Thetheir ratio may be normal even when an abnormal lambda immunoglobulin is showing up in the urine. Conversely, nearly 40 percent of patients have an abnormal ratio without having monoclonal gammopathy particularly those with the less-common lambda chain-associated lesions, could go undiagnosed because the serum free light chain test either is not picking up those abnormal proteins or the lambda lesions don’t make that many excess abnormal proteins.
Excessive light chains produced normally are easily excreted in the urine because of their small size. With monoclonal gammopathy, some of the excess light chains can get trapped in the kidneys and damage kidney function. Early symptoms of monoclonal gammopathy can be nonspecific, like feeling weak, and if it becomes cancer, one of the first symptoms may be a fractured bone because the cancerous cells have started consuming bone. Anemia, an increase in serum calcium and kidney failure are other symptoms.
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