Monoclonal gammopathy of undetermined significance (MGUS)

Overview

Monoclonal gammopathy of undetermined significance, also called MGUS, is a condition caused by the development of altered plasma cells. A plasma cell is a type of white blood cell that usually produces disease-fighting antibodies.

In MGUS, plasma cells in bone marrow produce antibodies called monoclonal proteins that circulate in the blood. These antibodies also may be called M proteins, myeloma proteins or paraproteins.

MGUS is not itself a disease, but having MGUS increases the risk of developing cancer of the plasma cells and related conditions.

There is no treatment for MGUS. With regular checkups, a healthcare team monitors for changes in M protein levels, increases in altered plasma cells, and signs of cancer or other diseases.

Symptoms

People with MGUS usually don't have symptoms. Most often, the condition is found with blood tests done for regular checkups or for diagnosing another condition.

Causes

Experts don't know what causes MGUS. Genes within plasma cells may change because of a number of factors.

Risk factors

Factors that increase your risk of developing MGUS include:

• Age. Most people with MGUS are 70 or older.
• Race. Black people and people of African descent have a higher risk of MGUS than do other people. People of Asian descent appear to have a lower risk than do others.
• Sex assigned at birth. MGUS is more common in men.
• Family history. A family history of MGUS is an increased risk.
• Immune system risks. Having a weakened immune system is linked to an increased risk.
• Chemical exposure. Exposure to toxic chemicals in the workplace or environment — such as pesticides, asbestos and fertilizers — may increase the risk of MGUS.
• Other factors. Risk factors that may be lessened with lifestyle changes include cigarette smoking and obesity.

Complications

Each year, about 1% of people with MGUS develop cancer of the plasma cells or related conditions. These include the following:

• Multiple myeloma is cancer of the plasma cells in the bone marrow. This results in poor blood cell production, weakened bones and bone pain.
• Waldenstrom macroglobulinemia is a cancer of the plasma cells that produces excessive M proteins. This may cause thickened blood, bleeding, frequent infections, and an enlarged liver and spleen.
• Lymphomas are cancers that begin in a part of the immune system called the lymph system. Excessive white blood cell production can affect multiple body systems.
• Light chain amyloidosis is the buildup of proteins derived from M proteins. These amyloid proteins often build up in the heart, kidneys and nerve cells outside the brain.

Monoclonal gammopathies of clinical significance

M proteins may cause disease in tissues and change how organs function. If this type of M protein–related condition develops, it's called monoclonal gammopathy of clinical significance. Affected areas of the body may include the:

• Kidneys.
• Nervous system.
• Eyes.
• Skin.

Other complications

Other complications include:

• Osteoporosis. People with MGUS have an increased risk of osteoporosis. This condition is the loss of bone tissue. It makes bones fragile and likely to break.
• Risk of infections. MGUS increases the risk of viral and bacterial infections, especially infections of the nose, throat and lungs.
• Thromboembolism. MGUS also increases the risk of blood clots that circulate in the bloodstream and can block the flow of blood to tissues. This blockage is called a thromboembolism.

Living with monoclonal gammopathy of undetermined significance (MGUS)?

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