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The myelodysplastic syndromes (MDS) are a group of diseases in which the production of blood cells by the bone marrow is disrupted.
In leukaemia, only the white blood cells are produced in excessively large numbers, whereas in MDS the production of any, and sometimes of all, types of blood cells is affected.
The myelodysplastic syndromes (MDS) are a group of diseases in which the production of blood cells by the bone marrow is disrupted. In leukaemia, usually only the white blood cells are produced in excessively large numbers, whereas in MDS the production of any, and sometimes of all, types of blood cells are affected. The bone marrow in MDS is usually more active than normal but there are fewer blood cells in the circulation. This is because most of the cells being produced in the bone marrow are poor quality (dysplastic) and are destroyed before they leave the bone marrow. This is the distinctive feature of MDS – the combination of overactive marrow with low blood cell counts. In about one third of patients with MDS, the disease transforms into acute myeloid leukaemia (AML) – this can occur within months or up to a few years. MDS is very rare in children and this information is about adult MDS only.
There is no known cause for MDS, but there are several risk factors which can increase the chances of getting the disease. These include:
No evidence exists to suggest that any infection increases the risk of MDS and it cannot be passed to other people.
About one in five (20%) of MDS patients have no signs or symptoms and are often diagnosed by chance as a result of a routine blood test. Low levels of healthy blood cells cause the main symptoms of MDS. These symptoms include:
You may not experience any of these symptoms at all. It is also worth remembering that these symptoms are often related to other conditions and do not always indicate MDS.
There are several classification systems for MDS, which are based on the appearance of the bone marrow and the blood cells. The newest classification system was developed by the World Health Organisation (WHO) and is recommended by the current UK Guidelines for Management of MDS.
There are seven types of adult MDS in the WHO system which are:
Cytopenia means too few cells in the blood and unilineage means that only one type of blood cell is reduced. There are three subtypes depending on which type of blood cell is affected. These are:
Refractory means that the condition does not improve with standard treatment such as iron for anaemia.
This is the same as refractory anaemia but there are red blood cells with ring shaped deposits of iron in them. These abnormal red cells are called ring sideroblasts.
This is like refractory anaemia but there is part of chromosome five missing (deletion) and with no other abnormalities of chromosomes in the affected cells. There is often a raised platelet count. This form is more often seen in female patients.
Refractory cytopenia with multilineage dysplasia (RCMD)
Multilineage means that more than one type of blood cell is affected. At least one cell type has low numbers and more than one cell type looks abnormal under the microscope (dysplasia). There may be ring sideroblasts present.
This is the same as refractory but there are at least 5% blasts (very immature blood-forming cells) in the marrow but fewer than 10%. There is dysplasia in most cases.
This is the same as refractory but there are at least 10% blasts (very immature blood-forming cells) in the marrow but fewer than 20%. If there are more than 20% blasts then it is classified as acute myeloid leukaemia. There is dysplasia in most cases.
There are some features in the blood and bone marrow samples which are seen in MDS but it does not fit any of the categories.
This is a condition in which patients have an abnormally high number of a type of white blood cells called monocytes in the blood. Because CMML patients have abnormal looking cells in their bone marrow, for a long time CMML was considered to be a type of MDS. However, it didn’t fit in well with other diseases in that category. Since CMML has features of both myelodysplastic syndrome and myeloproliferative disorder, experts created a new category for it: myelodysplastic/myeloproliferative diseases. The information in this factsheet does not apply to CMML; if you are diagnosed with this, you should ask your specialist or nurse to explain what this means.
There is also an International Prognostic Scoring System (IPSS) which has been to help doctors to predict how likely MDS is to progress to acute myeloid leukaemia (AML). The IPSS is used to help doctors decide what treatment to recommend.
The IPSS Score is determined by adding the individual scores for the percentage of blasts and for the cytogenetic and blood test findings, and is used to assess the clinical outcome for the MDS patient.
The IPSS Score indicates which of the following risk groups a patient falls into. A newer version is called the Revised IPSS (IPSS-R) and includes five risk groups, which are:
Very Low: IPSS-R score 0 to 1.5
Low: IPSS-R score more than 1.5 to 3
Intermediate: IPSS-R score more than 3 to 4.5
High: IPSS-R score more than 4.5 to 6
Very High: Greater than 6
MDS is diagnosed from blood tests and bone marrow examinations. The initial step in making a diagnosis of MDS is to have a full blood count (FBC). When the microscopic appearance of the blood cells suggest a diagnosis of MDS the doctor will then take a full clinical history of the patient and will take a sample of bone marrow to confirm the diagnosis. A bone marrow examination can reveal abnormalities in the cells of the marrow and also chromosomal abnormalities, such as missing or extra chromosomes. These tests provide additional information that can help in establishing the diagnosis. According to the British Committee for Standards in Haematology (BCSH) guidelines, ‘the diagnoses and classification of MDS remains dependent on the morphological examination’ (how cells appear under the microscope).
Not all patients with MDS will receive active treatment straightaway, but will have regular check-ups. This is referred to as watch and wait. The treatment that’s most appropriate for you will depend on the type of MDS you have, the IPSS-R risk group you’re in, your personal preferences and your general health. Most people with MDS have treatment at some point to control and improve the symptoms caused by low blood counts. This is called supportive treatment. Sometimes this may be the only treatment that’s needed if you’re in the low-risk category. The only treatment that is considered to be a cure is a donor stem cell transplant, although only a small minority of patients will be candidates for this type of treatment.
There are many different treatment options available if you have MDS. These include: