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Myelodysplastic syndrome (myelodysplasia)


Myelodysplastic syndrome (MDS) is a blood disorder that causes a drop in your number of healthy blood cells.

Another name for this condition is myelodysplasia.

What happens in MDS?

Normally, bone marrow produces:

  • red blood cells to carry oxygen around your body
  • white blood cells to help fight infection
  • platelets to help your blood to clot

In MDS, your bone marrow doesn't make enough healthy red blood cells, white blood cells and/or platelets. Instead, it makes abnormal cells that are not fully developed.

As the condition develops, your bone marrow becomes full of the abnormal blood cells, which spill out into your bloodstream.

MDS can either be indolent (slow developing) or aggressive (rapid developing).

The main types of MDS

The main types of myelodysplasia are:

  • refractory anaemia  just the red blood cells are affected
  • refractory cytopenia the red blood cells, white blood cells and platelets are affected
  • refractory anaemia with excess blasts (RAEB)  the red blood cells, white blood cells and platelets are affected, and there's a higher risk of developing acute leukaemia  

"Refractory" means the condition doesn't respond to treatment that doctors would normally use for low blood cell counts.

What are the symptoms?

For most people, symptoms are mild at first and slowly get worse. You may initially experience:

  • weakness, tiredness and occasional breathlessness  because of the low number of red blood cells
  • frequent infections  because of the low number of white blood cells
  • bruising and easy bleeding (such as nosebleeds) – because of the low number of platelets

Some types of MDS develop more quickly than others. Some people with MDS don't have any symptoms, and their condition is picked up after they have blood tests for something else.

Symptoms will depend on the type of MDS you have – for example, some people just have a problem with their red blood cells and have symptoms of anaemia, while others may lack all types of healthy blood cell.

Who is affected?

MDS can affect people of any age, but is most common in people aged 65-70 years. Only one in five people with MDS are younger than 50.

What are the causes?

In most cases, the cause is unknown – this is called primary MDS.

However, exposure to the chemical benzene used in the rubber industry, and found in petrol is known to increase your risk of developing MDS.

In rare cases, MDS is caused by radiotherapy or chemotherapy treatment for cancer. This is known as secondary MDS, or treatment-related MDS.

How is it diagnosed?

MDS is diagnosed by carrying out blood tests and bone marrow tests. Blood tests will show how many normal and abnormal blood cells you have.

A bone marrow test is done under local anaesthetic, which is injected into the area behind your hip bone. The doctor then passes a needle through your skin and into your bone, drawing out a sample of your bone marrow into a syringe. This will be sent to a laboratory to be examined under a microscope.

The bone marrow test takes 15-20 minutes and can be done on the ward or in the outpatients department.

Cancer risk

Some people with MDS go on to develop acute myeloid leukaemia (AML), which is cancer of the white blood cells. This is known as "transformation".

According to Cancer Research UK, the risk varies from five in every 100 cases (5%) to 65 out of every 100 cases (65%), depending on the type of MDS you have. It can take a few months or up to several years before transformation takes place.

Ask your doctor about your risk of developing AML.

How is MDS treated?

Treatment will depend on your type of MDS, your risk group, and whether you have any other health conditions.

The aim is to get the number and type of blood cells in your bloodstream back to normal, and manage symptoms with supportive treatment (see below).

If your MDS has only a low risk of transforming into cancer, you may not need any treatment at first, and may just be monitored with regular blood tests.

Supportive treatment

Symptoms of MDS can be controlled with a combination of the following treatments:

  • blood transfusion the drip may contain red blood cells or platelets, depending on which cells have been affected
  • drugs to get rid of the excess iron in your blood (which builds up after a lot of blood transfusions)
  • injections of growth factor drugs such as erythropoietin (which increases red blood cell count) or G-CSF (which increases white blood cells) to encourage your bone marrow to make more blood cells
  • antibiotics to treat infections, if your white blood cell count is low

Immunosuppression treatment

Drugs such as anti-thymocyte immunoglobulin (ATG) and ciclosporin reduce the activity of the immune system, allowing your bone marrow to make blood cells. It can also help to control symptoms.

However, these drugs are not suitable for everyone and work best in young people and those who don't have a chromosome change associated with their condition.


If you're at a higher risk of developing AML, you will need prompt treatment with chemotherapy or a stem cell transplant (see below).

Chemotherapy involves taking drugs that destroy the immature blood cells by disrupting their growth. The drugs are taken either as a tablet or an injection.

If you have a higher risk of developing AML, your chemotherapy treatment will probably be similar to that used to treat AML. Read about the treatment of AML.

You will probably have one or a combination of the following chemotherapy drugs:

  • cytarabine
  • fludarabine
  • daunorubicin
  • clofarabine
  • azacitidine (this is for people with higher-risk MDS who are unable to have a stem cell transplant)

Stem cell (bone marrow) transplant

The only way to cure MDS is to have intensive treatment with a stem cell transplant from a donor  but this isn't suitable for everyone.

A stem cell transplant will generally only be offered if you are young and in reasonably good health (apart from your MDS), as it's a very intensive treatment.

It helps if you have a suitable donor in your family (a close relative, such as a brother or sister), although in some cases, it's possible to have a stem cell transplant using an unrelated donor with a matching tissue type.

Treatment involves destroying your own bone marrow cells with chemotherapy and sometimes radiotherapy, before having stem cells from a donor fed into your bloodstream via a drip.

Read more about having a stem cell transplant.


The National Institute for Health and Care Excellence (NICE) recently published new guidelines on a biological therapy called lenalidomide. Biological therapies work by affecting the way your immune system functions.

Lenalidomide can be used to treat MDS in people with a specific genetic mutation, called an isolated deletion 5q cytogenetic abnormality.

This abnormality can lead to severe anaemia, which requires regular blood transfusions.

Read the NICE guidelines on lenalidomide for treating myelodysplastic syndromes associated with an isolated deletion 5q cytogenetic abnormality.

Clinical trials

The treatment of MDS is constantly evolving and new drugs are being tested all the time.

You may be offered the chance to enter a clinical trial. Find out more about:

Information about you

If you have MDS, your clinical team will pass information about you on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).

This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.

Find out more about the register.