Monoclonal gammopathy of undetermined significance (MGUS)

Date Updated: 07/22/2021

Overview

Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which an abnormal protein — known as monoclonal protein or M protein — is in your blood.

This abnormal protein is formed within your bone marrow, the soft, blood-producing tissue that fills in the center of most of your bones. The disorder occurs most commonly in older men.

MGUS usually causes no problems. But sometimes it can progress to more-serious diseases, including some forms of blood cancer.

If you have high amounts of this protein in your blood, it's important to have regular checkups so that you can get earlier treatment if it does progress. If there's no disease progression, MGUS doesn't require treatment.

Symptoms

People with monoclonal gammopathy generally don't experience signs or symptoms. Some people may experience a rash or nerve problems, such as numbness or tingling. MGUS is usually detected by chance when you have a blood test for another condition.

Causes

The precise cause of MGUS isn't known. Genetic changes and environmental triggers appear to play a role.

Risk factors

Factors that increase your risk of developing MGUS include:

Age. The average age at diagnosis is 70 years.
Race. Africans and African Americans are more likely to experience MGUS than are white people.
Sex. MGUS is more common in men.
Family history. You may have a higher risk of MGUS if other people in your family have the condition.

Complications

Each year about 1% of people with MGUS go on to develop certain types of blood cancers or other serious diseases such as:

Multiple myeloma
Light chain amyloidosis
Waldenstrom macroglobulinemia
Lymphoma

Other complications associated with MGUS include bone fractures, blood clots and kidney problems.

Diagnosis

Because MGUS usually causes no symptoms, it's usually detected by chance during blood tests for other conditions. Afterwards, your doctor may recommend:

More-detailed blood tests. These can help rule out other causes of elevated protein levels and can check for kidney damage.
Urine tests. A 24-hour urine collection can help determine if abnormal protein is being released into your urine. It can also assess any resulting kidney damage.
Imaging tests. If you are experiencing bone pain, your doctor might recommend an MRI or ositron emission tomography (PET) scan. The images can help your doctor find bone abnormalities related to MGUS. Your bone density also might need to be checked.
Bone marrow test. A hollow needle can remove a portion of your bone marrow from the back of one of your hipbones. Bone marrow analysis is generally done only when you're at risk of developing a more serious disease or if you have unexplained anemia, kidney failure, bone lesions or high calcium levels.

Treatment

MGUS doesn't require treatment. But your doctor is likely to recommend periodic checkups to monitor your health, probably starting six months after your diagnosis.

Watchful waiting

If you are at high risk of MGUS developing into a more serious condition, your doctor may recommend more frequent checkups so that any progression can be diagnosed and treatment started as soon as possible.

Your doctor is likely to watch for signs and symptoms such as:

Bone pain
Fatigue or weakness
Unintentional weight loss
Fever or night sweats
Headache, dizziness, nerve pain, or changes in vision or hearing
Bleeding
Anemia or other blood abnormalities
Swollen lymph nodes, liver or spleen

Medications

If you have osteoporosis, your doctor might recommend a medication to increase bone density. Examples include alendronate (Fosamax), risedronate (Actonel, Atelvia), ibandronate (Boniva) and zoledronic acid (Reclast, Zometa).

Preparing for an appointment

You may be referred to a doctor who specializes in blood disorders (hematologist).

It's a good idea to be well-prepared for your appointment. Here's some information to help you get ready, and what to expect from your doctor.

What you can do

List any symptoms you're experiencing, including those that may seem unrelated to the reason you scheduled the appointment.
List key personal information, including any major stresses or recent life changes.
List all medications, vitamins or supplements you take, including doses.
Ask a family member or friend to come with you. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
List questions to ask your doctor.

For MGUS, some basic questions to ask your doctor include:

What kinds of tests do I need?
Do these tests require any special preparation?
How frequently do I need to schedule follow-up visits and testing?
Do you recommend any treatment or lifestyle changes?
I have other health conditions. How can I best manage these conditions together?

Don't hesitate to ask other questions you have.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

Do you have any numbness or tingling in your hands and feet?
Do you have osteoporosis?
Do you have a family history of MGUS?
Have you ever had a blood clot?
Have you ever experienced a broken bone?
Have you ever had cancer?