Standard test for multiple myeloma provides clues of a rare, more deadly type

Investigators say even a test for the common blood cancer multiple myeloma gives clear indications that the patient has one of the most uncommon and deadly forms of this cancer.

Although there is a specific test for this rare IgD multiple myeloma, clues from the standard test are sufficient to initiate rapid aggressive treatment to reduce or prevent kidney destruction from excessive numbers of circulating proteins called light chains. Enough, Dr. Gurmukh Singh, vice president of clinical affairs for the department of pathology at the Medical College of Georgia.

Specific testing for IgD myeloma is available in some reference laboratories nationwide, but incurs additional time and expense that may not be necessary and may delay treatment initiation, Singh says.

IgD myeloma accounts for about 1% of multiple myeloma and has a worse prognosis, says study author Singh. International Journal of Pathology and Clinical Research,

With multiple myeloma, the plasma cells that normally produce a wide range of antibodies to help us fight infection, instead produce a single neutralizing antibody, called an M spike, that helps us fight infection. Makes us vulnerable to infection and can even attack our bones.

Usually the classic Y-shape of antibodies consists of two light chains, proteins that make up the Y arms with an antigen-binding site at their tips, where healthy antibodies bind to whatever they are attacking. The light chains are attached to the heavy chains, which separate, literally, the larger proteins that form the base of Y.

While more light chains are always produced with this blood cancer, especially with IgD, excessive numbers are produced that do not normally associate with heavy chains and consequently circulate freely in the blood and travel to the kidneys. who normally filter about half a cup of blood every minute, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

“The light chains are shorter, filtered out by the kidneys and ending up in the renal tubules,” says Singh, referring to the smaller tubes, where the kidneys filter nutrients, fluids, and blood. absorb other substances that have passed through and that can be rapidly injured. “You need to act quickly,” he says. “Dialysis with a special filter to capture light chains can prevent kidney damage and chemotherapy can further reduce the number of harmful light chains.”

In a retrospective review of more than 600 patients with multiple myeloma over 20 years at AU Medical Center, the MCG-affiliated adult teaching hospital, Singh and colleagues identified only four patients with the rare IGD multiple myeloma.

But the trial’s findings were consistent across all four and are a red flag for physicians that this IGD is likely myeloma and in urgent need of aggressive treatment, Singh says.

For example, a test commonly used in these patients is protein electrophoresis, which enables Singh to see in detail what plasma cells are creating based on their unique electrical charge. In all four patients with IgD myeloma, Singh found multiple bands indicating both neutralizing antibodies and excessive light chains, rather than just a single, solid band of color indicating the M spike that is characteristic of multiple myeloma. . They consistently indicated a specific type of light chain called a lambda, says Singh.

They write that these patients had almost three times the mortality rate compared to patients with other forms of this blood cancer. There were higher rates of kidney damage and dialysis in the 600 patients whose course he and his colleagues reviewed.

The IgD-specific test looks at heavy chains, says Singh, giving a more complete picture of the disease. He draws an analogy to a urine analysis that turns up a Gram-negative bacterium. The patient will go ahead and begin an antibiotic course but will still be given a test to determine the specific bacterium. Like that test for a specific bacterium, an IgD specific test usually won’t change, only delaying healing, Singh says.

Singh says next steps should include clinical trials comparing patient outcomes when IgD-specific tests are used and when these earlier indicators serve as clues to start treatment.

Singh reported last year in the journal lab medicine that patients producing these excessive levels of free light chains could potentially benefit most from early detection and intervention, including plasmapheresis to remove some of the circulating light chains from the blood, and dialysis kidneys to help filter them. For.

The wide range of non-specific symptoms for multiple myeloma, such as pain in your bones, weakness, fatigue, feeling very thirsty, frequent infections and fever, how often you urinate, confusion, etc. are similar across all types. According to the Multiple Myeloma Research Foundation, certain genetic mutations cause multiple myeloma, and men, especially black men, are at greater risk as are those over the age of 45.

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