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What is Myeloma?

Myeloma Basics

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Updated June 30, 2014

What is Myeloma?

Antibody image illustrating the heavy and light chains.

© 2006 Je at uwo

Myeloma is a blood cancer that involves the over-production of plasma cells, the antibody-producing cells that develop from B-lymphocytes in the bone marrow. Myeloma is also called multiple myeloma or plasma cell myeloma.

When plasma cells are exposed to a foreign substance, or antigen, they have the unique ability to create and excrete antibodies, or immunoglobulins, to help the body fight off infection. Immunoglobulins are proteins made up of heavy chains (G,A,M,D or E) and light chains (kappa or lambda).

In myeloma, there are mutations in the DNA of a single B-lymphocyte/plasma cell, which then begins to multiply out of control. These cancerous plasma cells are called myeloma cells.

As these malignant myeloma cells reproduce uncontrollably, they begin to crowd the bone marrow and prevent it from doing its normal job of producing healthy white cells, red cells and platelets. This leaves the patient with fewer cells to carry oxygen to their organs, form blood clots, or fight infection.

In addition, the myeloma cells will continue to produce the same immunoglobulins as the original cancerous cell. This leads to an excessive amount of one type of immunoglobulin (Ig), such as IgG or IgA being created. This abnormal immunoglobulin is unable to function like a normal antibody and help to fight infection. The accumulation of one type of immunoglobulin is called monoclonal protein (M-protein).

The myeloma cells will also invade bone tissue, causing damage and areas of weakness in the bone. Plasma cells and myeloma cells release chemicals called cytokines, which also contribute to bone destruction. As a result, myeloma patients will often have characteristic bone damage called osteolytic lesions.

Sources

Kyle, Robert and Rajkumar, S. Vincent "Multiple Myeloma" Blood 15 March 2008 111:2962-2972.

Lin, Pei "Plasma Cell Myeloma" Hematology/ Oncology Clinics of North America 2009 23:709-727.

Nau, Konrad and Lewis, William "Multiple Myeloma: Diagnosis and Treatment" American Family Physician 1 October 2008 78:853-859.

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