MGUS, short for monoclonal gammopathy of undetermined significance, is a condition that causes the body to create an abnormal protein. This protein is called monoclonal protein, or M protein. It’s made by white blood cells called plasma cells in the body’s bone marrow.

Usually, MGUS isn’t a cause for concern and has no adverse health effects. However, people with MGUS have a slightly increased risk of developing blood and bone marrow diseases. These include serious blood cancers, such as multiple myeloma or lymphoma.

Sometimes, healthy cells in the bone marrow can get crowded out when the body makes very large amounts of M proteins. This can lead to tissue damage throughout the body.

Doctors often recommend monitoring people with MGUS by performing regular blood tests to check for any signs of cancer or disease, which may develop over time.

MGUS usually doesn’t lead to any symptoms of illness. Many doctors find M protein in the blood of people with MGUS while testing for other conditions. Some people may have symptoms such as a rash, numbness, or tingling in the body.

The presence of M proteins in the urine or blood is one sign of MGUS. Other proteins are also elevated in the blood when a person has MGUS. These could be signs of other health conditions, such as dehydration and hepatitis.

To rule out other conditions or to see if MGUS is causing your health problems, a doctor may run other tests. These tests include:

  • Detailed blood tests. Some examples include a complete blood count, a serum creatinine test, and a serum calcium test. The tests can help check for an imbalance of blood cells, high calcium levels, and a decrease in kidney function. These signs are usually associated with serious MGUS-related conditions, such as multiple myeloma.
  • A 24-hour urine protein test. This test can see if M protein is released in your urine and check for any kidney damage, which could be a sign of a serious MGUS-related condition.
  • Imaging tests. A CT scan or MRI can check the body for bone abnormalities associated with serious MGUS-related conditions.
  • A bone marrow biopsy. A doctor uses this procedure to check for signs of bone marrow cancers and diseases associated with MGUS. A biopsy is usually only done if you show signs of unexplained anemia, kidney failure, bone lesions, or high calcium levels, as these are signs of disease.

Experts aren’t sure exactly what causes MGUS. It’s thought that certain genetic changes and environmental factors may affect whether or not a person develops this condition.

What doctors do know is that MGUS causes abnormal plasma cells in the bone marrow to produce M protein.

Many people with MGUS never end up having health issues related to this condition.

However, according to the Mayo Clinic, about 1 percent of people with MGUS develop a more serious health condition every year. The type of conditions that can develop depend on which type of MGUS you have.

There are three types of MGUS, each associated with an elevated risk of certain health conditions. These include:

  • Non-IgM MGUS (includes IgG, IgA or IgD MGUS). This affects the highest number of people with MGUS. There’s an increased chance that non-IgM MGUS will develop into multiple myeloma. In some people, non-IgM MGUS may lead to other serious disorders, such as immunoglobulin light chain (AL) amyloidosis or light chain deposition disease.
  • IgM MGUS. This affects about 15 percent of those with MGUS. This type of MGUS carries a risk of a rare cancer called Waldenstrom macroglobulinemia, as well as lymphoma, AL amyloidosis, and multiple myeloma.
  • Light chain MGUS (LC-MGUS). This has only been classified recently. It causes M proteins to be detected in the urine, and it can lead to light chain multiple myeloma, AL amyloidosis, or light chain deposition disease.

The diseases triggered by MGUS may cause bone fractures, blood clots, and kidney problems over time. These complications can make managing the condition and treating any associated diseases more challenging.

There’s no way to treat MGUS. It doesn’t go away on its own, but it doesn’t usually cause symptoms or develop into a serious condition.

A doctor will recommend regular checkups and blood tests to keep an eye on your health. Usually, these checkups start six months after first diagnosing MGUS.

Besides checking the blood for changes in M proteins, the doctor will look for certain symptoms that could indicate the disease is advancing. These symptoms include:

Because MGUS can lead to conditions that deteriorate bone mass, a doctor may recommend that you take a medication to increase your bone density if you have osteoporosis. Some of these medications include:

  • alendronate (Binosto, Fosamax)
  • risedronate (Actonel, Atelvia)
  • ibandronate (Boniva)
  • zoledronic acid (Reclast, Zometa)

Most people with MGUS don’t develop serious blood and bone marrow conditions. However, your risk can best be estimated by regular doctor visits and blood tests. Your doctor can also determine your risk of MGUS progressing into another disease by taking into account:

  • The count, type, and size of M proteins found in your blood. Larger and more numerous M proteins may indicate a developing disease.
  • The level of free light chains (another kind of protein) in your blood. Higher levels of free light chains are another sign of developing disease.
  • The age at which you were diagnosed. The longer you’ve had MGUS, the higher your risk of developing a serious disease.

If you or a loved one is diagnosed with MGUS, be sure to follow your doctor’s plans for monitoring your condition.

Staying on top of your MGUS can minimize your risk of complications. It can also increase your chances of a more positive outcome should you develop any MGUS-related disease.

Maintaining a healthy lifestyle can also lead to better outcomes. You can do this by getting enough sleep and exercise, reducing stress, and eating healthy foods such as fresh fruits and vegetables.