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What is MGUS and Why Is It Important to Monitor for It?

3 min read

What is MGUS and Why Is It Important to Monitor for It?

By: Bo Zhao, MD, PhD

Monoclonal gammopathy is a medical condition caused by abnormal proteins in the blood. These proteins grow from a small number of plasma cells, a type of white blood cell, found in the bone marrow. The most common condition linked with these abnormal proteins is monoclonal gammopathy of undetermined significance (MGUS). It is not cancer but does put these patients in a higher risk category for developing cancer in the blood or bone marrow.

MGUS is somewhat common, affecting about 3% of people over age 50. Risk for the condition, which is more common in men, climbs with age, reaching 3% for ages 60 to 69, greater than 4% for ages 70 to 79, and 6% for those ages 80 and above. 

MGUS can be a precursor of multiple myeloma or a lymphoma. Besides cancer, there are other medical conditions that can be caused by MGUS including nerve damage, kidney damage, or a weakened heart. 

How Do Doctors Identify MGUS in Their Patients?

MGUS is often diagnosed during the work up of chronic kidney disease (CKD) or peripheral neuropathy, through blood and urine testing. Sometimes identifying the problem can be difficult because the symptoms are very subtle, if seen at all, or could be associated with other conditions. For example, the worsening of chronic kidney disease may or may not be related to MGUS for patients with high blood pressure or high blood sugar, both of which are common causes of kidney disease.

Symptoms of MGUS

Most MGUS patients will experience no symptoms and will not progress on to cancer. The risk of progression to myeloma, for instance, is about 1% of MGUS patients a year. Because it may or may not transform into a cancer, watchful waiting is often the chosen approach. 

In case MGUS progresses to multiple myeloma, a bone marrow cancer, common problems include anemia, kidney damage, high blood calcium level, and bone fractures. For MGUS that progresses into lymphoma, symptoms may include a persistent low-grade fever, night sweats, or progressively enlarging lymph nodes. Some patients develop a bleeding tendency, disturbances in their vision, and neurologic symptoms.

In recent years, a novel concept of monoclonal gammopathy of clinical significance (MGCS) has been developed to provide some guidance for physicians. The National Comprehensive Cancer Network (NCCN) guidelines also included monoclonal gammopathy of renal significance (MGRS) and monoclonal gammopathy of neurologic significance (MGNS). Recognizing these categories and related findings will help physicians avoid missed cases of MGCS. 

Watchful Waiting for MGUS Patients

There is no specific treatment right now for MGUS. Rather, regular follow-up is done as part of watchful waiting. Visiting the doctor every three to six months is typically recommended. Each visit should include a physical exam, review of symptoms, as well as blood work and urinalysis to monitor changes. Depending on test results and protein levels in individual patients, the risk of progression to a cancerous condition can be determined. If at a higher risk, more frequent follow-up appointments may be recommended. 

If there are findings to suggest that MGUS starts to cause problems during watchful waiting, patients may receive further evaluation from one or more of the following types of physicians: a nephrologist (renal/kidney specialist), a neurologist (brain/spine and nerve specialist), and/or a hematologist (blood and bone marrow specialist). 

If you have been diagnosed with MGUS, be sure you have a regular check-up plan in place with a specialist such as a hematologist. The hematologists at Virginia Oncology Associates are available for a consultation to see if a watchful waiting program is right for you and to assess your risk for developing blood or bone marrow cancers.


Dr. Zhao is a Medical Oncologist and Hematologist at Virginia Oncology Associates, a regional practice that partners on clinical trials with the U.S. Oncology Network.