MGUS and the Multiple Myeloma Connection
Last updated: April 2023
Monoclonal gammopathy of undetermined significance (MGUS) is a medical condition characterized by increased levels of M protein in the blood. M (monoclonal) protein, also called a paraprotein, is produced by plasma cells. Plasma cells produce antibodies called immunoglobulins, which are proteins that attack foreign invaders and help the body fight infections.1,2
How does MGUS develop?
Plasma cells grow in bone marrow. In the normal process of white blood cell growth, plasma cells produce a variety of antibodies that can attack many different kinds of infections. But sometimes plasma cells produce too many immunoglobulins, leading to MGUS.1
MGUS most commonly affects people over age 50. Risk of MGUS is about 5% for people over age 75. The risk is higher for veterans who have been exposed to Agent Orange and certain other chemicals. People who are Black people and assigned male at birth also have a higher risk of developing MGUS.1,3
What are the symptoms of MGUS?
MGUS is a condition that may never produce any symptoms. One of the more common symptoms of MGUS is numbness or tingling in the hands and feet. This is called peripheral neuropathy.1
How is MGUS diagnosed and treated?
A diagnosis of MGUS is generally made when results from routine blood tests show an increase in protein levels. Urine tests can evaluate whether any excess protein is spilling over into the urine. Additional tests also may be requested.3
A doctor can monitor MGUS with periodic blood and urine tests. This will monitor for any changes in the protein levels in your blood. Treatment is generally not necessary for MGUS if there are no changes to the protein levels and you are not experiencing any symptoms. Many people live a long life with MGUS without ever developing serious symptoms or progressing to a more serious condition.3
MGUS and multiple myeloma
MGUS can be a precancerous condition. It can progress to different kinds of blood cancers including multiple myeloma and lymphocytic leukemia. Around 20% of people who have MGUS will eventually develop multiple myeloma. Most cases of multiple myeloma begin with MGUS.2,3
Multiple myeloma develops when a normal plasma cell mutates, or changes, into a myeloma cell. These myeloma cells can grow uncontrollably and develop into tumors inside and outside of the bone marrow. The disease is called multiple myeloma because tumors develop in multiple locations within the body. As the myeloma cells grow, they displace and break down good blood cells, like white blood cells that fight infection and red blood cells that carry oxygen throughout the bloodstream.2
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