MGUS: symptoms, what it means and how it is monitored

In most cases there are none. Blood Cancer UK says MGUS has no effect on how you feel physically, and Myeloma UK says most people will never know they have it. It is usually found when a blood test done for another reason picks up an abnormal protein.

Blood Cancer UK says a few people with MGUS have numbness or tingling in their hands and feet, or problems with their balance, which is a type of nerve damage (peripheral neuropathy) that is sometimes caused by the paraprotein in the blood. If you start having these symptoms or notice them getting worse, tell your doctor, who may refer you to a neurologist.

Plasma cells in the bone marrow normally make antibodies, which help the body fight infection. Blood Cancer UK explains that in MGUS some plasma cells make abnormal antibodies called paraproteins (also called monoclonal proteins or M-proteins). They do not work as well as normal antibodies and are not very good at fighting infection. Paraproteins and light chains circulate in the bloodstream and may show up in a blood test. In MGUS the levels are low and do not usually cause any health problems.

The name is a description. Blood Cancer UK says "monoclonal" refers to the abnormal antibodies being copies of each other, "gammopathy" to the production of abnormal antibodies, and "undetermined significance" to the fact that we do not yet know what causes it or why it progresses to blood cancer in a small number of people.

Myeloma UK says MGUS is a common condition that affects about 1 in 30 people over 50, rising to 1 in 20 over 70 and up to nearly 1 in 10 over 85. Blood Cancer UK gives a similar picture of about 3 in 100 people over 50, rising to around 5 in 100 over 70.

No. Blood Cancer UK says MGUS does not need treatment, but you will have regular check-ups. Myeloma UK says it is actively monitored but not treated, because many people with MGUS remain well and never develop any problems related to it.

The check-ups are the important part. Myeloma UK says people are usually checked every 3 to 4 months for the first year following diagnosis, and that checks can then be reduced to every 6 to 12 months as long as no symptoms develop. Blood Cancer UK says that if your results stay the same over time you may need check-ups less often or may not need them at all. You may be monitored by a haematologist, a specialist nurse or your GP.

At a check-up you have more blood tests, sometimes urine tests, and your doctor or nurse asks whether anything has changed in how you feel. You can ask for a printout of your results and ask your doctor to explain what they mean.

Blood Cancer UK says that if a blood test shows paraprotein in your blood your doctor will probably discuss the result with a specialist, and you may have more blood tests and sometimes scans to rule out myeloma, lymphoma or any other blood condition. The list below is from the same page.

• Blood tests to measure the type and level of paraprotein and light chains, to count the normal blood cells (full blood count), to check that your kidneys and liver are working properly, and to check the level of calcium.

• Urine samples, which can be checked for paraprotein and light chains.

• A bone marrow biopsy, which may be suggested if the paraprotein level in your blood is high, your full blood count or kidney tests are abnormal or you have some symptoms. It is normally done as an outpatient.

• X-rays, CT or MRI scans in some cases, to check for bone damage.

Occasionally. Blood Cancer UK says people with MGUS have a higher chance than normal of developing blood cancer, but it is rare for MGUS to turn into blood cancer. Research suggests that each year about 1 in 100 people (1%) with MGUS will develop blood cancer. If MGUS progresses, it usually develops into myeloma, and sometimes into a lymphoma called Waldenström macroglobulinaemia. Myeloma UK says MGUS can also progress to AL amyloidosis or lymphoma, and gives a figure that over a 10-year period about 10% (1 in 10) of people with MGUS will develop myeloma.

Your personal level of risk depends on the results. Blood Cancer UK says doctors look at the level and type of paraprotein, whether there is an abnormal ratio of kappa and lambda light chains, and sometimes the number of abnormal plasma cells in the bone marrow. IgG, the most common type, carries the lowest risk of progression. Ask your hospital team or GP what your own level of risk means for you.

Myeloma UK says there is not yet anything anyone can do to prevent MGUS from progressing. Blood Cancer UK says there is no evidence that lifestyle changes make a difference to whether it progresses.

Blood Cancer UK says we do not know what causes MGUS. You cannot catch it from someone else and it is not caused by your lifestyle. Myeloma UK says it is thought to involve complex changes at the genetic level. Several things make it more likely.

• Age. It becomes more common as people get older.

• Sex. It is more common in men than in women.

• Ethnic background. Blood Cancer UK says it is more common in Black people than in white people, and more common in white people than in people from an Asian background.

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

• Autoimmune conditions. Blood Cancer UK says it is widely thought to be more common in people with conditions such as rheumatoid arthritis, but that a recent study has questioned this, so the picture is not clear.

Usually with MGUS you will have no symptoms. But Blood Cancer UK says that if you notice any change in how you feel you should tell your doctor, as you may need more tests to find out whether it is caused by a change in the MGUS or by something else. Myeloma UK similarly lists fatigue, pain, recurrent or frequent infections and fractures as things to report.

• Pain in your back, ribs or hips for no apparent reason.

• Breathlessness.

• Extreme tiredness.

• Repeated infections.

• Generally feeling unwell or unable to do things you usually can.

• New or worsening numbness or tingling in the hands and feet, or balance problems.

Blood Cancer UK says that because MGUS affects your antibodies, you may be more likely than the general population to get infections from bacteria and viruses. It advises following standard hygiene and food safety advice and making sure you have all the recommended vaccinations, asking your GP if you are not sure which ones.

It also says there is no evidence that lifestyle changes affect whether MGUS progresses. The important thing is to go to your check-ups and report changes, and general NHS advice on healthy eating and exercise can help your wellbeing. On COVID-19, Blood Cancer UK says recent research suggests that having MGUS does not increase your risk of getting seriously ill, so people with MGUS are not recommended to take extra precautions unless they are in a high-risk group for another reason.

Living with a condition that has no treatment and can in a small number of cases develop into something more serious can be difficult, and Myeloma UK and Blood Cancer UK both offer information and support lines.

On the NHS, MGUS is usually picked up by a GP or hospital doctor through a blood test, then reviewed by a haematologist, and monitoring may be shared with the GP. Myeloma UK says you may be monitored by a haematologist, a specialist nurse or your GP. Ask the team who is responsible for your follow-up and when your next test is due.

Some people have the initial assessment or a second opinion privately. The tests and the monitoring approach described here are the same, and it helps to share results with your GP so that the record of your paraprotein levels stays in one place.