Monoclonal gammopathy of undetermined significance (MGUS)

Monoclonal gammopathy of undetermined significance, or ‘MGUS’, is a condition related to myeloma but it is not a cancer. Most people with will notice no effect on their general health.

MGUS is a common condition that affects about 1 in 30 people over 50. This increases with age, rising to 1 in 20 people over 70 and up to nearly 1 in 10 people aged over 85. Most people will never know that they have the condition because it does not usually cause any symptoms.

What is MGUS?

Monoclonal gammopathy of undetermined significance, or ‘MGUS’, is a benign (non-cancerous) condition. MGUS does not cause any symptoms and is usually diagnosed incidentally when tests are performed to investigate other problems. It does not require any treatment.

In MGUS, abnormal plasma cells in the bone marrow release an abnormal protein, known as paraprotein. MGUS is characterised by the presence of this abnormal protein in the blood and/or urine.

While most MGUS patients have a stable condition that has no effect on their general health, a small proportion of patients will go on to develop a cancer called myeloma. MGUS can also progress to other conditions such as Waldenström’s macroglobulinaemia, AL amyloidosis or lymphoma.

What causes MGUS?

The exact cause or causes of MGUS are not yet known but is thought to involve complex changes at the genetic level.

We do know that there are some risk factors that increase the chance of developing MGUS. The risk increases as people get older, it’s more common in men and in people from Black ethnic groups than white or Asian, and more common among people with a close relation with the condition.

How is MGUS diagnosed and what are its symptoms?

MGUS is not associated with any symptoms, so the abnormal protein is usually discovered when tests are being performed to rule out other health issues. Once the abnormal protein is discovered, it is important to make sure that it is not due to a more serious diagnosis such as myeloma, and so further tests are likely to be carried out.

How is MGUS managed?

MGUS is actively monitored but not treated. This is because many patients with MGUS remain well and never develop any problems related to it. However, a very small number of people with MGUS go on to develop another, more serious condition. For example, over a 10-year period, 10% of people (1 in 10 people) with MGUS will develop myeloma (a blood cancer). For this reason, it is important to have regular blood tests to check for any change in your condition. Regular checks will make sure that if you need treatment, you can have it as soon as it is necessary.

MGUS patients are usually checked every 3-4 months for the first year following diagnosis. The checks can then be reduced to every 6-12 months as long as no symptoms develop.

You may be monitored by a haematologist, a specialist nurse or by your GP.

We have a free MGUS Diary for patients, where you can keep a record of your test results and learn more about how MGUS is monitored. Click on the link below to find out more.

How will I know if my MGUS is progressing?

Your healthcare team will monitor you for any signs that your MGUS may be developing into another condition.

They will look at trends in your results and any symptoms you have. Keeping an eye out and reporting any symptoms, including fatigue, pain, recurrent or frequent infections, and fractures, will help them build a full understanding of your condition.

There are certain risk factors that may increase the chance of it progressing, although the risk still remains very low.

If you are worried about the potential for MGUS to progress into another condition, make sure you get the support you need through your healthcare team or by getting in touch with us.

Can I prevent MGUS progressing?

There is not yet anything anyone can do to prevent MGUS from progressing to another condition.

We’re working to understand what may cause people with MGUS to develop myeloma.

Living with MGUS

Living with a condition for which there is no treatment or cure and that can, in a small number of cases, develop into something more serious can be difficult. Get the support you need by getting in touch.

What is MGCS and MGRS?

Monoclonal gammopathy of clinical significance (MGCS) and monoclonal gammopathy of renal significance (MGRS) are conditions similar to MGUS. MGCS and MGRS are not cancer.

Unlike in MGUS, in MGCS and MGRS, the paraprotein causes symptoms or complications. Most commonly these are kidney problems (MGRS), peripheral neuropathy (a problem with the nerves), or skin symptoms

In a very small number of cases, MGCS and MGRS can develop into other conditions, such as myeloma.

People with MGCS or MGRS will be monitored for any change in their condition and symptoms and complications will be treated as needed.

In some cases, you may receive treatment for the underlying abnormal plasma cells if necessary.

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Speak to one of our Myeloma Information Specialists

If you need information, emotional support, practical advice or just a listening hear, our Myeloma Information Specialists are here for you. You can call them on 0800 980 3332 (Mon – Fri, 9-5) or email them on