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What is monoclonal gammopathy of undetermined significance (MGUS)?
By Robert A. Kyle, MD

The finding of a monoclonal protein or MGUS means that there is an abnormal protein that has been detected in your blood tests. Typically this protein is found during a routine physical examination and is identified using a screening blood test called “protein electrophoresis.” This protein by definition is not associated with more serious problems that are typically associated with protein abnormalities such as multiple myeloma. The source of this protein is a small population of plasma cells in the bone marrow. Plasma cells are present in the bone marrow of all normal adults and represent approximately 1% of all of the bone marrow cells. Plasma cells’ normal function is to produce antibody proteins that help protect your body against infection.

On mass screening, the finding of an abnormal protein in the blood is not rare. In fact, 2% of adults over the age of 50 will have this as an incidental finding during screening examinations. However, the frequency with which these proteins are found rises as we age. At age 70 the incidence is from 3 to 4%. The finding of this abnormal protein will occur in both sexes and in all races and is not limited based on occupation or background.

The finding of an abnormal protein in the blood (MGUS) will not produce any symptoms. Detecting an abnormal protein is generally not a concern and extensive testing is generally not required unless there are symptoms that warrant a greater index of suspicion on the part of your physician. Follow-up is required for all patients indefinitely, and your physician will monitor protein levels regularly.

The protein noted above is found on a serum protein electrophoresis test; when this test is performed, the blood protein is separated into five component proteins. The monoclonal protein graphically will look like a peak or spike. Physicians often refer to this as a blood spike and, again, this finding may not require any additional testing if there are no other pertinent physical findings or symptoms.

Treatment for monoclonal gammopathy is not required, although research protocols are in existence for patients at centers that specialize in the treatment of monoclonal gammopathy and multiple myeloma. The reason why these proteins are a concern is that patients who have them have a higher risk of developing a more serious blood or bone marrow problem such as multiple myeloma. Fully 80% of patients with a protein abnormality will never develop any problems related to it. However, because 20% of patients might go on to develop problems, careful follow-up is required. This may only require an annual blood test. This blood test, protein electrophoresis, can be done in virtually any hospital laboratory. For most individuals, a bone marrow examination is not required. More in-depth testing may be done if the protein level has changed or if symptoms develop.

It must be kept in mind that a monoclonal gammopathy does not represent cancer. However, because patients with monoclonal proteins are at risk of developing multiple myeloma or related disorders, lifelong monitoring is required. The presence of the protein, since it is derived from bone marrow plasma cells, is not impacted by your diet or the amount of protein you consume, since dietary protein and the production of monoclonal proteins are unrelated. There is no increased risk of monoclonal gammopathies in first-degree family members; therefore, your siblings and children do not need to be screened for the presence of an abnormal protein.

In summary, the finding of a monoclonal gammopathy is not an indication for treatment, generally does not require invasive testing, and is not a cause for overt concern. One must be prudent, however, since there is a risk, albeit small, that patients with monoclonal proteins could develop more serious disorders. Close monitoring will allow your physician to intervene before problems occur. Therefore, annual testing is appropriate.




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