Monoclonal gammopathy of undetermined significance (MGUS) is a rare condition caused by an overabundance of a certain protein in your blood. Monoclonal gammopathy doesn't cause any signs and symptoms. Your doctor may have discovered your monoclonal gammopathy coincidentally during a blood test for some other disease or condition.

Monoclonal gammopathy is more common in adults over age 50. Monoclonal gammopathy occurs more frequently in men and in black people.

Monoclonal gammopathy raises concerns because it can progress to become a more serious condition, such as multiple myeloma or another cancer, in some cases. Doctors have difficulty predicting who will go on to develop a more serious disease and who won't. For this reason, people with monoclonal gammopathy usually undergo annual checkups to look for signs that their condition is progressing to something more serious.

Monoclonal gammopathy of undetermined significance causes no signs or symptoms.

Monoclonal gammopathy of undetermined significance is one of four types of monoclonal gammopathies. These conditions occur when plasma cells in the bone marrow multiply out of control, creating an overabundance of a certain naturally occurring protein called a gamma globulin. The protein that's being overproduced is sometimes called a monoclonal protein or M protein.

If you have monoclonal gammopathy of undetermined significance, your body is overproducing the M protein, but not enough to hurt you. In other types of monoclonal gammopathies, such as multiple myeloma, too much M protein accumulates, crowds out healthy cells in your bone marrow and can damage structures within your body.

Factors that increase your risk of monoclonal gammopathy of undetermined significance include:

• Your age. The condition is more common in older adults.
• Your race. Blacks are more likely to experience this condition than are whites.
• Your sex. Monoclonal gammopathy of undetermined significance is more common in men.

Monoclonal gammopathy of undetermined significance is usually detected during a blood test for another condition. The test, called serum protein electrophoresis (SPEP), separates your blood proteins into five parts and can show any abnormal proteins.

If your doctor detects monoclonal gammopathy, he or she may order further testing to determine what M protein your body is making and how much is being made. Your doctor also works to rule out other causes of elevated protein levels. Tests may include:

• Blood tests. Tests to count the blood cells in your blood (complete blood count), to look for decline in kidney function (serum creatinine test) and to determine the amount of calcium in your blood (serum calcium test) can help rule out other types of monoclonal gammopathy, such as multiple myeloma.
• X-rays. X-rays of bones throughout your body help your doctor look for bone abnormalities that may indicate you have another type of plasma cell disorder.
• Bone marrow test. During a bone marrow test, your doctor uses a hollow needle to remove a portion of your bone marrow from the back of one of your hipbones. Your doctor analyzes your bone marrow to determine what percentage of cells are plasma cells.

About 20 percent of people with monoclonal gammopathy of undetermined significance develop a more serious condition, including cancers such as multiple myeloma and non-Hodgkin's lymphoma. Most people never develop a more serious condition.

Doctors can't predict who will go on to develop a more serious condition, but they can determine who's at the greatest risk. Your doctor takes into account several factors when determining your risk of a more serious condition, including:

• The amount of M protein in your blood
• The type of M protein
• The number of plasma cells in your bone marrow

Your risk of developing a more serious condition increases the longer you've had monoclonal gammopathy of undetermined significance. Studies have found that people who develop a more serious condition do so an average of about 10 years after their initial diagnosis.

Monoclonal gammopathy of undetermined significance doesn't require treatment. However, because of the risk that the condition may develop into something more serious, your doctor may recommend frequent checkups to monitor your health.

Ask your doctor what type of tests you should have and how often they should be performed. An annual checkup may be appropriate for most people. If you have a high risk of developing a more serious condition, your doctor may recommend more frequent checkups. Tests may include bone marrow exams, blood tests and X-rays, among others.

No way exists to prevent monoclonal gammopathy of undetermined significance. Once you have the condition, there is no treatment to prevent it from progressing to a more serious condition.

Not knowing whether your condition will worsen or remain stable can cause anxiety. You might worry about your health and fear for your future. Though you can't control whether your monoclonal gammopathy will worsen, you can control many aspects of your health. Learn to cope by trying to:

• Learn what you can about monoclonal gammopathy. Write down any questions that come up and ask your doctor about them during your next appointment. Ask your health care team about resources for more information. The better you understand what's going on in your body, the more you'll be able to take an active role in your health care.
• Control what you can about your health. Living a healthy lifestyle won't reduce your risk of complications in the future, but it can make you feel better about yourself and reduce your risk of other diseases and conditions. Eat a variety of fruits and vegetables. Get regular exercise. Get enough sleep so that you wake feeling rested. Reduce the amount of stress in your life.
• Stick to your checkup schedule. Follow your doctor's checkup schedule and get the tests to check for more-serious diseases. Though you might be nervous about receiving your test results, diagnosing a serious condition, such as cancer, early may improve your chance for a cure.