Monoclonal gammopathy of unknown significance (MGUS)

MGUS Back to top

MGUS is a condition that affects a type of white blood cell known as a plasma cell. The blood contains three different types of blood cells:

• red blood cells carry oxygen around the body
• white blood cells are part of the body’s immune system, helping to fight infection and disease
• platelets help the blood to clot and prevent bleeding.

Plasma cells are a type of white blood cell that produce special proteins, known as antibodies or immunoglobulins. These antibodies circulate in the blood, ready to attack any viruses and bacteria that may be present in the body.

When an abnormally large amount of one particular antibody is produced, this is called monoclonal gammopathy. All the antibodies are identical.

Sometimes, monoclonal gammopathy is called paraproteinaemia. The individual antibody that is being produced in large amounts is called an M-protein.

Monoclonal gammopathy of unknown significance (MGUS) is a non-cancerous (benign) condition. The levels of antibody in MGUS, although raised, are not as high as the amount produced in people with myeloma (cancer of the plasma cells) and some types of lymphoma (cancer of the lymphatic system). If someone has raised antibody levels but no evidence of either of these types of cancer, their condition is known as monoclonal gammopathy of unknown significance (MGUS).

MGUS can occur at any age, but is more common in older people. It affects one in 100 of people over 50, and 3 in 100 of people over 70. It can affect men and women, of any occupation or background. The cause is unknown.

Signs and symptoms Back to top

Most people with MGUS (approximately four out of five) remain well and never develop any symptoms related to it.

Sometimes, MGUS can be associated with non-cancerous conditions such as inflammation, arthritis or infection.

There is a risk that a small number of people with MGUS might go on to develop cancers affecting the blood after a few years. The type of cancer depends on the kind of M- protein that's present in the blood.

These cancers include myeloma, lymphoma, Waldenstrom’s macroglobulinaemia|, and amyloidosis.

Possible symptoms of these might be: feeling very tired|; repeated coughs; colds and other infections; unexplained bruising or bleeding; swollen lymph glands; pain|; night sweats; and weight loss.

Diagnosis Back to top

MGUS is often discovered by accident, when routine blood tests are taken for other conditions. The diagnosis is confirmed by a particular blood test called a serum electrophoresis test, which identifies the abnormal antibody. The doctor looks to see whether there is an abnormally high amount of a particular antibody being produced. This is sometimes referred to as a blood spike.

Other tests will also be considered to exclude other more serious conditions. These may include a bone marrow examination, x-rays of the bones, and further blood and urine tests.

Follow-up and treatment Back to top

As MGUS does not cause any symptoms in most people, it does not require any treatment. However, because of the small risk of developing cancer it is important to have regular check-ups. This involves blood tests to monitor your M-protein levels, which can change over time. Doctors will look at the trend of the M-protein levels – whether they are generally stable, or steadily rising.

If your M-protein levels are gradually rising, or if you have any symptoms that are causing your doctor concern, they may want to carry out the tests mentioned earlier, or repeat them for comparison if they have previously been done.

References Back to top

This section has been compiled using information from a number of reliable sources including:

• Oxford Textbook of Oncology (2nd edition). Eds Souhami et al, Oxford University Press, 2001.
• Wintrobe's Clinical Haematology (12th edition) Eds Lee et al, Williams and Wilkins, 2008.

For further references, please see the general bibliography|.