Medical Edge Newspaper Column

MGUS: A Common But Typically Harmless Blood Disorder

May 1, 2009
Dear Mayo Clinic:
Can you tell me if there is any cure or even some type of relief for MGUS?

Answer:
Monoclonal gammopathy of undetermined significance (MGUS) is a blood disorder that occurs when there is overgrowth of identical plasma cells in bone marrow. Since it is the job of any given plasma cell to make a single (monoclonal) immunoglobulin protein, an increased population of identical bone marrow plasma cells may be detected by discovery of a monoclonal protein (M protein) in the blood stream. Rarely, MGUS can be a precursor to cancer, such as multiple myeloma, or other serious blood disorders. But for most people, MGUS is harmless and doesn't cause symptoms or require treatment.

MGUS is a common condition that becomes more prevalent with age. About 3 percent of people 50 and older and 5 percent of those 70 and older have M protein in their blood. The highest incidence is among adults age 85 and older. And MGUS is more common in men than in women.

Typically, MGUS is found during a blood test that's done for another reason. The test, called a serum protein electrophoresis, can reveal abnormal proteins and unusual amounts of normal proteins.

A doctor who detects monoclonal gammopathy may recommend further testing to determine what type of M protein the body is making and how much. The tests can also help a doctor rule out other medical conditions that may be causing production of M protein.

If the doctor determines that the presence of M protein isn't the result of an underlying medical condition, then, typically, monitoring suffices for MGUS follow-up care. Although MGUS has no cure, the condition rarely causes symptoms, and usually no treatment is necessary.

However, in a minority of cases, over time the cells in bone marrow that make M protein can accumulate, crowding out healthy cells. Or, the M protein can damage other tissues in the body. In this situation, treatment with chemotherapy may be necessary. The risk of developing a more serious condition increases the longer a person has had MGUS. There is about a 1 percent per year risk of developing a significant problem.

People who have MGUS usually require a yearly evaluation including a blood test to monitor changes in their level of M&nbps;protein and to check for other symptoms. Some who are at low risk of developing a more serious disorder may require monitoring less frequently. The frequency of checkups depends on the size and type of M protein the body is producing, as well as a person's medical history. If you've been diagnosed with MGUS, talk to your doctor about establishing an appropriate follow-up schedule.

— Angela Dispenzieri, M.D., Hematology, Mayo Clinic, Rochester, Minn.