Monoclonal Gammopathy of Undetermined Significance (MGUS)

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.

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.