Monoclonal Gammopathy of Undetermined Significance (MGUS)

Overview

What is monoclonal gammopathy of undetermined significance (MGUS)?

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.

Who is most at risk for getting monoclonal gammopathy of undetermined significance (MGUS)?

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:

  • African-American
  • Exposed to pesticides
  • Male
  • Part of a family with a history of MGUS or multiple myeloma

How common is monoclonal gammopathy of undetermined significance (MGUS)?

Rates of MGUS climb with age. Up to 5% of people aged 70 or older are eventually diagnosed with MGUS.

Symptoms and Causes

What causes monoclonal gammopathy of undetermined significance (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.

What are the symptoms of monoclonal gammopathy of undetermined significance (MGUS)?

MGUS usually causes no symptoms. In rare cases, people may have:

  • Tingling
  • Weakness
  • Numbness

Diagnosis and Tests

How is monoclonal gammopathy of undetermined significance (MGUS) diagnosed?

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.

Management and Treatment

How is MGUS treated?

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.

What complications are associated with monoclonal gammopathy of undetermined significance (MGUS)?

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.

Prevention

Can monoclonal gammopathy of undetermined significance (MGUS) be prevented?

There is no way to prevent MGUS.

Outlook / Prognosis

What are the outcomes after treatment for monoclonal gammopathy of undetermined significance (MGUS)?

For most people, MGUS does not require treatment and never causes complications.

Living With

When should I call my doctor in regard to monoclonal gammopathy of undetermined significance (MGUS)?

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.

Last reviewed by a Cleveland Clinic medical professional on 03/08/2018.

References

  • International Myeloma Foundation. Monoclonal Gammopathy of Undetermined Significance (MGUS) and Smoldering (Asymptomatic) Multiple Myeloma: IMWG Consensus Perspectives Risk Factors for Progression and Guidelines for Monitoring and Management. (https://www.myeloma.org/imwg/mgus-smoldering-multiple-myeloma--consensus-risk-factors) Accessed 3/19/2018.
  • Multiple Myeloma Research Foundation. What Are MGUS, Smoldering Myeloma, and MM? (https://www.myeloma.org/what-are-mgus-smm-mm) Accessed 3/19/2018.
  • Genetic and Rare Diseases Information Center. Monoclonal Gammopathy of Undetermined Significance. (https://themmrf.org/multiple-myeloma/what-is-multiple-myeloma/) Accessed3/19/2018.
  • Merck Manual Professional Version. Monoclonal Gammopathy of Undetermined Significance (MGUS). (http://www.merckmanuals.com/professional/hematology-and-oncology/plasma-cell-disorders/monoclonal-gammopathy-of-undetermined-significance-mgus) Accessed 3/19/2018.
  • Leukemia Foundation. Monoclonal Gammopathy of Undetermined Significance (MGUS). Accessed 3/19/2018. (http://www.leukaemia.org.au/blood-cancers/myeloma/mgus)
  • Leukemia & Lymphoma Society. Monoclonal Gammopathy of Undetermined Significance (MGUS) Facts. (https://www.lls.org/sites/default/files/file_assets/MGUS_FINAL.pdf) Accessed 3/19/2018.

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