Monoclonal gammopathy of undetermined significance (MGUS) is a precancerous condition that affects plasma cells. A patient with MGUS has an increased risk of developing blood cancer, such as myeloma or lymphoma.
However, the risk is relatively low. About 1% of those with MGUS develop cancer, as suggested in follow-up studies conducted every year on these patients.
What is monoclonal gammopathy?
Monoclonal gammopathy is a condition in which plasma cells produce abnormal proteins that spill over in the blood.
Plasma cells are a type of white blood cell that produce antibodies to fight infections in the bone marrow.
The abnormal protein produced by plasma cells is called M-protein or a paraprotein. It is called monoclonal because even if it is made by several cells, they are identical and produced by one family of cells.
What are the symptoms of monoclonal gammopathy?
Usually, most patients with MGUS may not experience any symptoms at all (benign monoclonal gammopathy).
However, some patients may present with symptoms such as:
What are the risk factors of monoclonal gammopathy?
The exact cause of MGUS is unclear, but experts believe that it may be caused by a combination of genetic changes and environmental factors.
Age is the most significant risk factor of monoclonal gammopathy MGUS. M-protein is found in the blood of about 3% of adults ages 50 and older; 5% of those are 70 and older. Adults 85 and up make up most cases.
Other risk factors include:
How is monoclonal gammopathy diagnosed?
Because monoclonal gammopathy causes few or no symptoms, the condition is usually diagnosed during routine blood and urine tests that show the presence of M-protein. To confirm a diagnosis, a serum electrophoresis test is recommended to confirm the presence of the abnormal M-protein.
Following a diagnosis, the patient may be subjected to a series of tests to determine the status and progression of the disease:
- Bone marrow biopsy: A small sample of bone marrow is aspirated and tested to detect the number of affected plasma cells in the bone marrow.
- 24-hour urine test: Urine is collected during a 24-hour period and checked for the total amount of M-protein.
- Blood tests: Blood tests are done to check for the amount of M-protein in the blood. Functionality tests of major organs, especially the kidneys, may be done as well.
- Radiological imaging: Radiological imaging tests, such as computed tomography, magnetic resonance imaging, positron emission tomography, etc., are done to detect complications such as osteoporosis and cancer development.
What are the treatment options for monoclonal gammopathy?
Most patients with MGUS do not require therapy, although others may require therapy in the future. People with MGUS should undergo blood and urine testing every 6-12 months to see if the disease is progressing.
Although no active therapy is required for MGUS, regular monitoring is advised through clinical assessments and serum protein measurements. To establish a definitive diagnosis of MGUS, the serum protein should be tested after 3 months and then again after 6 months. If the paraprotein has stayed steady, it should be tested every year after that. As there is a chance of developing osteoporosis, medications to improve bone density may be recommended.
MGUS may progress to specific forms of blood cancers in a small percentage of people:
Treatment for such patients depends on the type and stage of cancer. Annual follow-up is recommended to scan for the development of any abnormalities.
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Mouhieddine TH, Weeks LD, Ghobrial IM. Monoclonal gammopathy of undetermined significance. Blood. 2019; 133 (23): 2484-2494. https://ashpublications.org/blood/article/133/23/2484/273836/Monoclonal-gammopathy-of-undetermined-significance
Roswell Park. What Is MGUS? - Monoclonal Gammopathy of Undetermined Significance. https://www.roswellpark.org/cancer/multiple-myeloma/about/mgus