The Connection Between MGUS, Lupus, and Rheumatoid Arthritis

Living with lupus or rheumatoid arthritis calls for constant learning. There is much to know about these complex illnesses, varying treatment options, and ways to improve quality of life. People with rheumatic conditions find they are also at risk for other disorders, including monoclonal gammopathy of undetermined significance (MGUS).

What is MGUS?

MGUS is a disorder of the plasma cells, which live in the body’s bone marrow. Plasma cells play a key role in immunity. These cells create antibodies or proteins (also called immunoglobulin) that protect the body from illness.¹

In MGUS, the plasma cells produce too many copies of matching proteins called monoclonal proteins. A certain amount (<3 g/dL) of these monoclonal proteins exist in people with MGUS. The plasma cells can also multiply in MGUS but make up no more than 10 percent of cells in the bone marrow.^1-3

People with MGUS have no noticeable signs to alert them of the disorder. The increase in proteins and plasma cells does not usually affect organ function or result in symptoms. Doctors often detect MGUS when these raised levels appear on blood tests that people undergo for other reasons.^1-3

While doctors have not found what triggers MGUS, they must keep an eye on this disorder. Some types of MGUS can quickly advance and become blood cancers, including amyloidosis, lymphoma, and multiple myeloma.^1-3

Rates and risk factors for MGUS

MGUS is the most common plasma cell disorder. MGUS accounts for 67 percent of all plasma cell disorders. Light chain amyloidosis, smoldering multiple myeloma, and solitary plasmacytoma are other plasma cell disorders.^1,3

Several factors increase a person’s risk of MGUS. Gender is one of those factors. MGUS affects more men than women.³

Research also shows that older adults have a higher rate of MGUS. The rate ranges between 3.2 and 5.1 percent in people ages 50 and above. One study found the rate as high as 7.5 percent in people ages 85 and above.³

Rheumatic conditions

Studies have also revealed a link between MGUS and rheumatic conditions like lupus and rheumatoid arthritis.

A study published in 2007 showed that monoclonal gammopathy (MG) occurs more often in people with lupus than in those without lupus. Out of 1,083 people in the study, 59 people (about 5 percent) had MG. Although cancer was found in 15.3 percent of those with MG, the rate was not much higher than in those without MG.⁴

A 2018 study assessed 41 people with MG and rheumatic diseases such as lupus and rheumatoid arthritis. More than 50 percent of the people had increased disease activity. Cancer was found in 17.1 percent of those in the study.⁵

MGUS does come with a risk of developing blood cancer. However, blood cancers form in only 1 percent of people with MGUS every year.^1,3

How is MGUS treated?

People with MGUS do not require treatment. However, if MGUS progresses to blood cancer, treatment is needed and may include chemotherapy and other drugs.^1,3

Doctors recommend continual monitoring and regular testing for people with MGUS. Tests can track blood counts and levels of calcium, monoclonal proteins, and plasma cells. The goal is to check for anything that points to blood cancer, such as bone lesions, cell overgrowth, and kidney issues.^1,3,5

How often a person with MGUS needs to undergo testing depends on their level of risk. The International Myeloma Working Group and European Myeloma Network agree that a follow-up exam should occur 6 months after diagnosis. After that, future exams may occur yearly or every 2 to 3 years.³

Monitoring all aspects of our health

People with lupus and rheumatoid arthritis learn to look out for many things. Among them are signs of a flare-up and disease progression, as well as other disorders like MGUS. The presence of MGUS calls for even more careful watching.

Knowing your condition is one of the best ways to protect your health. Having lupus and/or rheumatoid arthritis comes with added risks like MGUS. Your doctor can help you monitor all aspects of your health and recommend treatment as needed.