27 May 2022

A standard test used for multiple myeloma can also help identify if a patient might have one of the most uncommon and deadly forms of the blood cancer, a US study has suggested.

A researcher at the Medical College of Georgia, Augustus, says while there is a specific test for rare IgD multiple myeloma, standard testing could yield sufficient results to enable the start of aggressive treatment to reduce or prevent kidney destruction.

Writing in the International Journal of Pathology and Clinical Research, Dr Gurmukh Singh, vice chair of clinical affairs for the Department of Pathology at the Medical College of Georgia, said his findings mean treatment for IgD myeloma could begin sooner before the results of the specific test can confirm the diagnosis.

In a retrospective review of more than 600 patients with multiple myeloma over 20 years at AU Medical Center, Dr Singh identified only four patients with the rare IgD multiple myeloma.

But, he writes, standard test findings were consistent in all four and are a red flag to physicians that the patient is likely to have IgD myeloma, which necessitates urgent and aggressive treatment.

The plasma cells that normally produce a wide range of antibodies to help fight infection produce an M spike when someone has multiple myeloma.

In normal antibodies, the Y-shape has two light chains. These are the proteins that form the arms of the Y with an antigen-binding site on their tips. These light chains hook up with heavy chains, which are larger proteins that form the base of the Y.

While multiple myeloma produces more light chains, particularly the IgD form, excessive numbers are produced that do not link to heavy chains. These move freely about in the blood and inundate the kidneys, the researcher said.

Dr Singh said: “Light chains are small, get filtered by the kidneys and end up in the renal tubules. You need to act quickly. Dialysis with a special filter to capture light chains can prevent kidney damage and chemotherapy can further reduce the number of damaging light chains.”

In this study, Dr Singh examined the protein electrophoresis test, looking in detail at what plasma cells make based on the unique electrical charge of their proteins.

In all four patients with IgD myeloma, he found multiple bands that reflect dysfunctional antibodies and the excessive light chains, rather than just the single, solid band of colour that depicts the M spike. These also consistently indicated more lambda, a specific type of light chain.

Dr Singh said the next step is to have clinical trials that compared patient outcomes when the IgD specific testing is used and when the standard testing serves as a presumptive diagnosis.

Source: Singh G. “Criteria for Presumptive Diagnosis of IgD Multiple Myeloma.” International Journal of Pathology and Clinical Research, doi: 10.23937/2469-5807/1510125

Link: https://clinmedjournals.org/articles/ijpcr/international-journal-of-pathology-and-clinical-research-ijpcr-8-125.php

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