In monoclonal gammopathy of undetermined significance (MGUS), blood samples contain abnormal proteins called monoclonal proteins, or M proteins. Plasma cells in the bone marrow (the soft substance at the center of bones) produce M proteins.
Normally, plasma cells produce antibodies that help your body fight infection. But people living with MGUS have plasma cells that produce unusual proteins (M proteins) instead of normal antibodies. In most cases, M proteins do not cause any problems.
MGUS itself is benign (not cancer), and most people have no symptoms. Doctors and other healthcare providers usually diagnose the condition after taking blood or urine samples as part of a routine examination. Most patients with MGUS do not need treatment. Some patients may need treatment in the future. People with MGUS need to be monitored with blood and urine testing every 6 to 12 months to determine if MGUS is progressing.
For a small percentage of individuals, the condition develops into cancerous conditions, such as multiple myeloma or lymphoma.
MGUS is more common in older individuals. Individuals over the age of 50 years have a 3-5% chance of having MGUS. The highest incidence is in people age 85 or older. You may be more likely to develop MGUS if you are:
Rates of MGUS climb with age. Up to 5% of people aged 70 or older are eventually diagnosed with MGUS.
MGUS results from abnormal plasma cells in bone marrow producing abnormal proteins called M proteins. Usually, plasma cells produce antibodies, which are specialized proteins that help identify and defend your body against germs. Each plasma cell produces only one type of specialized protein, or antibody.
People living with MGUS have abnormal plasma cells in addition to healthy plasma cells. These abnormal plasma cells produce M proteins instead of antibodies. M proteins circulate in the blood. They can be detected in blood and urine tests.
MGUS usually causes no symptoms. In rare cases, people may have:
In most cases, doctors and healthcare providers diagnose MGUS when blood or urine samples are evaluated as part of routine medical examination, or when patients have unexplained symptoms of pain, low red blood cell counts (called anemia), or kidney problems.
Most people with MGUS do not need treatment. Your doctor or healthcare provider will monitor your blood M-protein levels every 6 to 12 months. Monitoring M-protein levels allows your doctor to determine if your condition is changing. Doctors and healthcare providers especially watch to see if MGUS develops into another problem, like multiple myeloma.
For a small percentage of individuals, MGUS progresses into certain types of blood cancers, including multiple myeloma, certain lymphomas, or a rare condition called amyloidosis. Also, the condition raises the risk of bone loss and bone fractures in some people. In cases where bone loss happens, your doctor or healthcare provider might tell you to take bone strengtheners to improve bone density.
There is no way to prevent MGUS.
For most people, MGUS does not require treatment and never causes complications.
If you are age 50 or older, ask your doctor about checking for MGUS as part of your next routine health examination. If you develop symptoms such as numbness or tingling, let your doctor know.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 03/08/2018