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April 8, 2020

Rare Genetic Mutation Could Complicate Diagnosis of Lymphoid Disorders

By Sara Tiner

A report by Mayo researchers adds a new wrinkle to the diagnosis of lymphoid malignancies. The case report in the Journal of Allergy and Clinical Immunology is focused on one patient and protein used by the immune system, called an antibody.

Antibodies are Y-shaped proteins produced by a sub-group of white blood cells called B lymphocytes. They flood the blood, stick to their target (bacteria, viruses), marking them for “clean up” by other cells of the immune system. The Y-shape has two components: light chains and heavy chains. Together, the light and heavy chains make the two arms of the Y, whereas the base is only made by the heavy chain.

“The study describes a patient who lacks the kappa light chain, the main form of light chain in human antibodies,” explain Amir A. Sadighi Akha, M.D., D.Phil. and Maria A. V. Willrich, Ph.D. The two are immunologists at Mayo and corresponding authors of the paper. “This was a chance finding in the patient’s serum, and prompted the more specialized tests performed afterwards.”

Left to Right: Dr. Sadighi Akha and Dr. Willrich. Their work on complete kappa light chain absence is published in the Journal of Allergy and Clinical Immunology.

The absence of the kappa light chain does not increase the risk of infection, but it can lead to abnormal lab findings. The most important of these is the possibility of diagnosing a patient with B lymphocyte cancer by mistake.

“So far, only 3 patients with kappa light chain absence, including ours, have been reported in the world, but recent estimates suggest that at least 300 people in the United States could have this condition”, say the authors. “Therefore, pathologists should have this condition in mind when evaluating a patient for B lymphocyte disorders."

Going forward, the authors will work on making physicians aware of this diagnostic possibility in patients being evaluated for B lymphocyte disorders.

In addition to Drs. Willrich and Sadighi Akha, other authors are Renee Tschumper, B.S.; John Mills, Ph.D.; Crescent Isham, B.S.; Elizabeth Witty, MS; David Viswanatha, M.D.; Surendra Dasari, Ph.D.; Melissa Snyder, Ph.D.; David Murray, M.D., Ph.D.; Jerry Katzmann, Ph.D.; and Diane Jelinek, Ph.D.

No funding entities supported this work. The authors disclose one conflict of interest: David Murray, John Mills, and Surendra Dasari have intellectual property and receive royalties related to the analysis of immunoglobulins by mass spectrometry.

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Tags: Amir Sadighi Akha, antibodies, B Lymphocyte disorders, Diane Jellinek, Maria Willrich, News

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