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Monoclonal gammopathy of undetermined significance (MGUS)

Medically reviewed by Last updated on Aug 1, 2023.


Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which an atypical protein is found in the blood. The protein is called monoclonal protein or M protein.

This protein is made in the soft, blood-producing tissue in the center of bones. This blood-producing tissue is bone marrow. Monoclonal gammopathy of undetermined significance occurs most often in older men.

MGUS usually causes no problems. But sometimes it can lead to more-serious diseases. These include some forms of blood cancer.

People who have high amounts of this protein in the blood need regular checkups. That's so they can get earlier treatment if the condition gets worse. If it doesn't get worse, MGUS doesn't need treatment.


People with monoclonal gammopathy often don't have symptoms. Some people have a rash or nerve problems, such as numbness or tingling. A blood test for another condition might find MGUS by chance.


Experts don't know what causes MGUS. Changes in genes and being around certain chemicals, such as those used to kill pests, appear to play a role.

Risk factors

Factors that increase your risk of developing MGUS include:


Each year, about 1% of people with MGUS get certain types of blood cancers or other serious diseases, such as:

Other issues linked to MGUS include broken bones, blood clots, kidney problems, and damage to nerves outside of the brain and spinal cord, also known as peripheral neuropathy.


Because MGUS usually causes no symptoms, people who have it usually find out by chance during blood tests for other reasons. After that, other tests might include:


MGUS doesn't require treatment. But your health care provider is likely to have you get regular checkups to watch the condition. Checkups likely will start six months after your diagnosis.

Watchful waiting

For those at high risk of MGUS leading to a more serious condition, more-frequent checkups can watch the disease. That way, treatment can start as soon as possible if it's needed.

Symptoms to watch for include:


Medicine for the bone-thinning disease known as osteoporosis increase bone mass. Examples include alendronate (Fosamax), risedronate (Actonel, Atelvia), ibandronate and zoledronic acid (Reclast, Zometa).

Preparing for an appointment

Your health care provider might refer you to someone who specializes in blood disorders, also known as a hematologist.

Here's information to help you get ready for your appointment.

What you can do

Ask a family member or friend to go with you. Someone who's with you can help you remember the information you get.

Make a list of:

For MGUS, basic questions to ask your provider include:

Be sure to ask all the questions you have.

What to expect from your doctor

Your health care provider is likely to ask you questions, including:

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