We're here for you if you want to talk

0808 2080 888

[email protected]

MGUS (monoclonal gammopathy of undetermined significance)

We're here for you if you want to talk

0808 2080 888

[email protected]

What is MGUS?

MGUS is a blood condition that affects blood cells called plasma cells. It is not in itself a type of blood cancer, but there is a small risk that MGUS can develop into a type of blood cancer.

MGUS is often diagnosed after a blood test to investigate another health condition. In most cases, people with MGUS have no symptoms and will never need treatment. The chance of MGUS developing into blood cancer is low.

Understanding MGUS

In our bone marrow (the spongy tissue inside certain bones), we have cells called plasma cells. These cells make antibodies – Y-shaped proteins that help our bodies fight infection. They are sometimes called gamma globulins or immunoglobulins.

If you have MGUS, some of your plasma cells make abnormal antibodies called paraproteins (also known as monoclonal proteins or M-proteins). Paraproteins don’t work as well as normal antibodies and aren’t very good at fighting off infection.

Sometimes, the abnormal plasma cells only make small pieces of an antibody called light chains.

A digram showing the structure of an antibody

Paraproteins and light chains circulate in the bloodstream and may show up in a blood test. In MGUS, the levels are low and don’t usually cause any health problems.

MGUS itself is not blood cancer but people with MGUS do have a higher risk than normal of developing blood cancer in the future. Overall, the risk is low. Your personal level of risk depends on the levels and types of paraprotein and light chains in your blood, so your GP or hospital team will measure and monitor these.

Front cover of MGUS (Monoclonal gammopathy of undetermined significance) - your questions answered, in red with a large burgundy logo.

Free booklets about MGUS

Our MGUS booklet answers the key questions you, your family and friends may have.

Order your free copies now

Types of MGUS

There are five types of paraprotein: IgG, IgA, IgM, IgD and IgE. Ig stands for immunoglobulin, another name for paraprotein.

There are two types of light chain: kappa (κ) and lambda (λ). So when you get an MGUS diagnosis, you might be told the type is IgG lambda, for example. Occasionally the abnormal protein in the blood is just a kappa or lambda light chain, and no paraprotein is present. This is called light chain MGUS.

Your plasma cells will only produce one type of paraprotein. IgG is the most common type and also carries the lowest risk of progression to blood cancer.

It’s best to ask your doctor about your personal level of risk.

How common is MGUS?

In the UK, around 6,000 people are diagnosed with MGUS every year.

Many people with MGUS are completely unaware of it, as they have no symptoms and it doesn’t affect how they live their life.

Find out more from other people with MGUS

Users are discussing their MGUS experiences and sharing tips on our community forum. Check out the latest forum threads:

What causes MGUS?

We don’t know what causes MGUS. We do know that you can't catch it from someone else and it’s not caused by your lifestyle.

Certain things make it more likely for someone to have MGUS:

MGUS gets more common with age. It affects about three in a hundred people (3%) over 50 years old, rising to around five people in a hundred (5%) over 70 years old.

MGUS is more common in men than women.

MGUS is more common in Black people than white people, and more common in white people than people from an Asian background.

It is widely thought that MGUS is more common in people with diseases such as rheumatoid arthritis which involve the immune system (the organs and cells that fight infection). A recent study has questioned this, so the picture is not clear.

MGUS is thought to be more common in people who have a relative with MGUS, myeloma or another blood cancer.

What does MGUS mean?

MGUS is an abbreviation for the medical term monoclonal gammopathy of undetermined significance.

Monoclonal: This describes the abnormal antibodies in MGUS, which are clones or copies of each other.

Gammopathy: Gammopathy refers to the production of abnormal antibodies (which scientists call gamma globulins).

Undetermined significance: (or sometimes, unknown significance) This acknowledges that we don’t yet know what causes MGUS and why it progresses to blood cancer in a small number of people.

Sign up to our newsletter

Get the latest news from Blood Cancer UK direct to your inbox

An error occured. Please try again later.

We will keep you updated about our work and the ways you can help, including campaigns and events. We promise to respect your privacy and we will never sell or swap your details.

Many thanks to Dr Simon Stern and Dr Kamaraj Karunanithi for checking the accuracy of our information about MGUS.

We're here for you if you want to talk

0808 2080 888

[email protected]