Myelodysplastic syndrome (MDS) is a blood disorder that causes a drop in your number of healthy blood cells. This typically results in weakness, frequent infections and/or bleeding problems.
These symptoms can happen gradually or rapidly (see What are the symptoms? below).
Another name for this condition is 'myelodysplasia', where 'myelo' means 'bone marrow' (the soft material in the middle of bones) and 'dysplasia' means 'abnormal growth'.
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 does not 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.
Your blood then becomes full of the abnormal blood cells that don't function properly, rather than healthy blood cells. It is this low level of normal blood cells that is responsible for symptoms.
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.
Also, the 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 your low numbers of red blood cells
- frequent infections, because of your low numbers of white blood cells
- bruising and easy bleeding (such as nosebleeds) because of your low numbers of platelets
However, some people with MDS don't have any symptoms, and their condition is picked up after blood tests for something else.
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 not known – this is called primary MDS.
However, we do know that exposure to the chemical benzene – used in the rubber industry, and found in petrol – increases your risk of developing MDS.
Rarely, MDS is caused by 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.
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 your 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 (see box on this page), you may not need any treatment at first, and may just be monitored with regular blood tests.
Symptoms of MDS can be controlled with a combination of the following treatments:
- a blood transfusion – the drip may contain red blood cells, white 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
Drugs such as anti-thymocyte immunoglobulin (ATG)and ciclosporin reduce the activity of the immune system, allowing your bone marrow to make blood cells, and can help to control symptoms.
However, these drugs are not suitable for everyone and work best in those who are young and who do not have a chromosome change associated with their condition.
The above links will take you to more information on these medicines.
If your risk of developing cancer is 'intermediate' or high, 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.
You will probably have one or a combination of the following chemotherapy drugs:
- azacitidine (this is for people with higher-risk MDS who are unable to have a stem cell transplant)
The above links will take you to more information on these drugs, including their side effects.
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 is not suitable for everyone.
A stem cell transplant is very intense treatment that will generally only be offered if you are young and in reasonably good health (apart from your MDS).
It helps if you have a suitable donor in your family (a close relative such as a brother or sister), although some patients can 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.
The treatment of MDS is constantly evolving and new drugs are being tested all the time. One drug currently being tested for MDS is the biological drug lenalidomide.
Biological therapies work by affecting the way your immune system works.
You may be offered the chance to enter a clinical trial and try lenalidomide. This is given on its own if you have low-risk MDS, or in combination with chemotherapy if you have high-risk MDS.
Find out more about joining a clinical trial.