Monoclonal gammopathy of undetermined significance, more commonly known as MGUS, is a condition in which an abnormal protein called monoclonal protein is present in the bloodstream. Monoclonal proteins, or M proteins, are produced by abnormal plasma cells in the bone marrow. Normal, healthy plasma cells are white blood cells that produce antibodies to help us fight infections.

MGUS is not a malignant disorder, and it causes no symptoms or damage to the body. However, approximately 1 percent of people diagnosed with MGUS progress each year to more serious illnesses such as myeloma or amyloidosis, and these can certainly be dangerous and require treatment.

Treatment is not appropriate for people with MGUS. Instead, doctors will recommend observation — usually with testing every six to 12 months to monitor the condition.

To learn more about MGUS, MyMyelomaTeam talked with hematologist-oncologist Dr. James Hoffman, assistant professor of clinical medicine at the Sylvester Comprehensive Cancer Center, University of Miami. His focus is on plasma cell disorders, including monoclonal gammopathy of undetermined significance.

Risk Factors for MGUS

Some people are more likely to develop MGUS than others. According to Mayo Clinic, four factors indicate a higher risk of MGUS:

• Older age (the biggest risk factor)
• African or African-American ethnicity
• Male sex
• A family medical history of MGUS

From Benign to Malignant

Dr. Hoffman described plasma cell disorders as a continuum, with monoclonal gammopathy of undetermined significance at the mild end. “MGUS requires observation,” he said. “Multiple myeloma requires treatment. That’s the spectrum from benign to malignant within the world of plasma cell diseases.”

MGUS affects the people who have it in different ways. Many say one of their most significant concerns is that the condition will progress into a more serious condition, such as multiple myeloma.

Some members of MyMyelomaTeam do experience progression from MGUS to multiple myeloma, in which cancerous plasma cells accumulate in the bone marrow. “I was first diagnosed with MGUS in 2014,” wrote one member. “In late 2015, after a [bone marrow] aspiration, I was told it became full multiple myeloma.” Another member said, “After ongoing monitoring, I have started treatment for multiple myeloma.”

However, most people diagnosed with MGUS live with the condition without it ever developing into smoldering multiple myeloma or multiple myeloma. “My sister has had it for five years or so,” one member shared. “They check her labs every six months — no signs of active myeloma.” Another wrote, “I have been diagnosed with MGUS since 1996. … I have not been diagnosed with myeloma or any other condition.”

Although MGUS is a benign condition, it still requires regular checkups. The critical health concern is the abnormal protein level in the blood and, in the case of MGUS, there’s very little. On the other hand, in myeloma, those cells grow and cause damage, making it essential for people to keep tabs on the condition with the guidance of their health care providers.

Monitoring and Blood Tests

Dr. Hoffman explained that people with MGUS could have their need for treatment prioritized based on their risk factors. Of those with MGUS at the lowest risk for progression, only about 0.5 percent per year have their condition become more serious. People with higher-risk MGUS may have up to a 3 percent annual risk for progression and need to be watched more carefully.

“Generally speaking, having low levels of these abnormal cells in the bone marrow, having low levels of the protein in the blood, those are two really critical variables,” Dr. Hoffman said. “That tells you the burden of the illness is very, very low. If there’s a higher amount of cells, then the risk is higher.”

In many cases, successful monitoring of MGUS can be accomplished with blood work alone. This spares people the type of unpleasant or invasive testing that can make them reluctant to become diligent partners in their own treatment. Blood tests used to monitor MGUS commonly include a complete blood count, a comprehensive metabolic profile, serum protein electrophoresis, and serum free light chains, among others.

“People don’t need repeated bone marrow biopsies or repeated scans,” Dr. Hoffman said. “Again, thankfully, the majority of people will never need treatment, so we try not to overtest those patients.”

Moving Forward After MGUS Diagnosis

Living with MGUS can still cause anxiety, even if the risk of progression to multiple myeloma is low. “My husband was diagnosed with MGUS three years ago,” a spouse on MyMyelomaTeam shared. “So far, his labs are good, but it scares me to death.” She added, “We see the oncologist every six months, even though they say once a year is enough. But I want to keep an eye on things.”

The small percentage of people with MGUS who develop multiple myeloma generally do somewhat better than those who didn’t realize they had MGUS before they developed myeloma. “I had MGUS for 12 years prior to diagnosis with multiple myeloma,” a member shared. “I understand the odds are it won’t move on to MM from MGUS, but if you stay in contact with your oncologist, you have a better chance of catching it early.”

Dr. Hoffman agreed that keeping an eye on things is a big part of making sure MGUS does not progress into something more serious. At the same time, he wanted to make sure people understand that outcomes for MGUS vary, and many people never see it turn into something more serious.

“Remember, wherever you are on that spectrum, the majority of patients will not die of this problem,” he said. “It does require vigilance, you do need to have follow-ups, and you don’t want to allow something to occur without paying attention to it. But again, for the majority of people, it's a benign condition.”

By joining MyMyelomaTeam, the social network and online community for those living with myeloma, you gain a support group more than 16,000 members strong. Living with MGUS is one of the most-discussed topics.

How does MGUS affect your daily life? How often does your doctor monitor your symptoms? Share your experiences in a comment below or on MyMyelomaTeam. You’ll be surprised how many other members have similar stories.