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 (pronounced para-proteen-eem-ia). 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 1 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.

Most people with MGUS (approximately 4 out of 5) 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. These include myeloma, lymphoma, Waldenström's macroglobulinaemia, and amyloidosis.

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

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, and further blood and urine tests.