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If your bone marrow produces dysplastic blood cells, many of these cells will die before or soon after they reach the bloodstream, and those that do reach it don’t work properly. This means you don't have enough healthy blood cells.

In some people only one type of blood cell is affected, but sometimes all of the blood cells will be low (this is called pancytopenia).

MDS is a form of bone marrow cancer. It can sometimes develop into acute myeloid leukaemia (AML).

The treatment options for MDS vary a lot from person to person, depending on the symptoms you're having and the type of MDS that you have. Some people with MDS won't need treatment, but others may need high-intensity treatment such as a stem cell transplant.

What are myelodysplastic syndromes (MDS)?

Myelodysplastic syndromes, or MDS for short, are a group of diseases in which the production of blood cells by the bone marrow is faulty. It is a type of cancer and sometimes may be referred to as bone marrow failure.

The bone marrow is the factory where blood cells are made. In MDS, it is here where the problem lies.

The bone marrow makes three main types of blood cells:

  • red blood cells that carry oxygen around the body,
  • white blood cells that fight infections, and
  • platelets that prevent bleeding.

In MDS, the bone marrow is usually more active than normal, yet the cells it produces are not healthy (dysplastic) and many die either before they reach the bloodstream or shortly afterwards. This results in the number of blood cells in the bloodstream being reduced. In addition, those cells that are circulating in the blood do not work as well as they should. Some patients have just one type of blood cell that is low (such as red blood cells), but sometimes MDS can cause a reduction in all the types of blood cells. This is called ‘pancytopenia’.

In addition to low blood counts, the myelodysplastic syndromes share a common tendency to develop into acute myeloid leukaemia (AML) over time. The risk of this occurring depends on the type of MDS, and some patients with early forms of the disease may never progress to AML.

What causes MDS?

MDS is a rare disease. It may be diagnosed at any age but it is very rare in childhood and young adults.

The typical age for patients to develop MDS is around 75 years old. About nine out of 10 patients are over 50 years at the time of diagnosis. Men are slightly more likely than women to be diagnosed with MDS.

The cause of MDS remains largely unknown, although there are many research groups around the world who are trying to improve our understanding of why it occurs and in whom. There are certain factors that may increase your chance of developing MDS and these include: 

  • Previous chemotherapy with or without radiotherapy – this treatment may have been given in the past, usually for other cancers. It is thought that the treatment damages the bone marrow factory cells and may cause MDS in some patients. This is called secondary or therapy-related MDS, as it is secondary to the previous chemotherapy or radiotherapy. 
  • Inherited disorders – very rarely, MDS can be inherited or may develop from another rare blood disorder such as Fanconi anaemia. For this reason, young patients may be tested for any diseases that are linked to MDS. However for the vast majority of patients, MDS will not be passed down to children and is not an inherited genetic disease. 
  • Environmental factors – exposure to toxic chemicals such as benzene may marginally increase the risk of MDS, but such exposure is now uncommon.

MDS is not an infectious disease and it cannot be passed on to other people.

What are the types of MDS?

There are many types of MDS and this can be difficult to understand. Spend time talking to your doctor or nurse so you understand how your MDS will be treated.

There is a generally accepted classification system for separating the different types of MDS. A ‘classification’ is broadly a means to describe the type of MDS that we see down the microscope. This system is based on the blood results, the appearance of the bone marrow and any chromosome changes found. The World Health Organization (WHO) has developed a regularly updated classification based on the appearance of the bone marrow and the number of leukaemia cells seen. These leukaemia cells are called blasts, which may be increased in some of the types of MDS. 

There are six broad types of MDS included in the current classification (2008), these are: 

  • refractory cytopenia with unilineage dysplasia (RCUD), 
  • refractory anaemia with ring sideroblasts (RARS), 
  • refractory cytopenia with multilineage dysplasia (RCMD), 
  • refractory anaemia with excess blasts (RAEB),
  • myelodysplastic syndrome unclassified (MDS-U), and 
  • MDS associated with del(5q), including the 5q- syndrome. 

The terminology used can be difficult to understand, so ask your doctor to explain which type of MDS you have. Low blood counts are called ‘cytopenias’, ‘dysplasia’ means that the bone marrow cells are abnormal in their appearance, and ‘sideroblasts’ are young red cells that have a very distinctive ring of iron granules seen under the microscope. There is a special type of MDS recognised by the fact that the chromosome tests show part of the chromosome five is missing. It is referred to as del(5q).

High-risk and low-risk MDS

It is often easier to consider whether the type of MDS you have falls into what is called a LOW risk group or a HIGH risk group. The ‘risk’ refers to your chance of developing acute myeloid leukaemia (AML) and your life expectancy (survival). In the low-risk disease group a patient has about a one in 10 chance of progressing to AML. The low-risk group includes RCUD, RARS, RCMD, MDS-U and the 5q- syndrome.

In contrast, the risk of developing leukaemia is greater in the high-risk disease group (RAEB). The separation into these groups is important as the treatment of patients with low-risk and high-risk disease can differ.

Why is chronic myelomonocytic leukaemia (CMML) not included in the MDS classification?

CMML tends to behave in one of two ways; either like MDS, or like myeloproliferative neoplasms (MPN), where some of the blood counts are high rather than low. The WHO has therefore classified it separately. Most patients with CMML have a high white blood cell count and often an enlarged spleen.

> You can find more information on CMML here

Signposting and useful contacts

Many people affected by MDS find it useful to call on the expert information, advice and support offered by a variety of organisations, including Bloodwise. Here are some other sources of help that we recommend.

There are a number of UK centres with a specialist interest in treating patients with MDS, some of which are recognised as Centres of Excellence. You can request to be referred to these specialists for an additional opinion and a referral request can be made via your GP or your local haematologist. These referrals are particularly helpful for the more complex MDS cases.

Additional opinions are sought by many patients across the UK. These are perfectly reasonable requests, given that MDS is a rare and complex disease. Although all haematologists will be familiar with the condition, not all of them will have the specific expertise found in specialist centres. After you are seen at a specialist centre for your additional opinion, you will still be treated at your local hospital and your local haematologist will work together with the specialist to provide you with optimal care.

A specialist centre will also provide you with a dedicated clinical nurse specialist (CNS). You will be able to consult your CNS between appointments if necessary.

The specialist centres for MDS include:


King’s College Hospital, London – Professor Ghulam Mufti

St James’s Institute of Oncology, St. James’s University Hospital, Leeds – Professor David Bowen

Royal Bournemouth Hospital, Bournemouth – Dr Sally Killick

Queen Elizabeth Hospital, Birmingham – Professor Charles Craddock, Dr Manoj Raghavan

Brighton and Sussex University Hospital, Brighton – Dr Tim Chevassut, Dr Christopher Dalley

MRC Laboratory, Addenbrookes NHS Trust, Cambridge – Professor Alan Warren

University of Oxford Cancer and Haematology Centre, Oxford – Professor Paresh Vyas

Christie Hospital, Manchester – Dr Mike Dennis

Newcastle Centre for Cancer Care – Dr Gail Jones

Nottingham University Hospital – Dr Emma Das-Gupta

Great Western Hospitals NHS Foundation Trust, Reading – Dr Alex Sternberg

Royal Cornwall Hospitals Trust, Truro – Dr Anton Kruger

Worcestershire Acute Hospitals NHS Trust and Birmingham NHS Foundation Trust – Dr Juliet Mills

St Bartholomew’s Hospital, London – Dr Jamie Cavenagh

Northampton General Hospital – Dr Jane Parker


Aberdeen Royal Infirmary – Dr Dominic Culligan

Beatson West of Scotland Cancer Centre – Dr Mark Drummond


University Hospital of Wales, Cardiff – Dr Jonathan Kell


Adelaide and Meath Hospital, Dublin – Dr Helen Enright

UK patient organisations and support groups


MDS UK Patient Support Group provides information, assistance and advice to patients and families affected by myelodysplastic syndromes.

Leukaemia CARE

Leukaemia CARE is dedicated to providing information, support and advice to blood cancer patients, their carers and loved ones.


We offer patient information online and in free printed booklets, and have an online community you may like to join.

We can help with practical and emotional support and signpost you to other available services.


Provides a helpline, information on all types of cancer, financial advice and travel insurance recommendations.

Anthony Nolan

Provides information specifically to patients, families and stem cell donors regarding stem cell transplantation and donation.

Maggie’s Centres

Maggie’s offers free practical, emotional and social support to people with cancer and their families.

International patient organisations and support groups

MDS Support Group Ireland (& Northern Ireland)

MDS Foundation

International information and support group based in the USA. Provides further information on MDS, and contact with American MDS patients via a chat forum.

Aplastic Anaemia and MDS International Foundation

International organisation supporting patients and families living with aplastic anaemia, myelodysplastic syndromes (MDS), paroxysmal nocturnal haemoglobinuria (PNH), and related bone marrow failure diseases.

Financial assistance and benefits advice

Macmillan Support Line

  • 0808 808 0000

Your local Citizens Advice Bureau


Travel insurance

While it can often be difficult to get travel insurance if you have a pre-existing medical condition such as MDS, you can still go on holiday. Macmillan Cancer Support provides information about what to consider when looking for travel insurance, along with recommendations from their online community.

For carers

Carers UK

Carers Trust

Patient Information Forum member NHS Information Standard certified member