Myelodysplastic syndromes are a group of diseases in which the bone marrow doesn’t make enough healthy mature blood cells. The immature blood cells, called blasts, do not work properly. They build up in the bone marrow and the blood. As a result, there are fewer healthy red blood cells, white blood cells and platelets.
Myelodysplastic syndromes usually develop in older people. They develop more often in men than in women.
Some people with a myelodysplastic syndrome have a change, or mutation, in the JAK2 (Janus kinase 2) gene. People with a myelodysplastic syndrome often have changes in certain chromosomes. Chromosome changes that are found in people with myelodysplastic syndrome include:
- a deletion (loss) of the q-arm in 1 or more of chromosomes 5, 7 and 20
- complete deletion of chromosome 5 or 7
- an extra copy of chromosome 8
When a myelodysplastic syndrome develops without any known cause, it is called de novo myelodysplastic syndrome.
Myelodysplastic syndromes can progress to acute myeloid leukemia in about one third of people.
In the past, myelodysplastic syndromes were classified as a disease of low malignant potential and referred to as a pre-leukemia. Now that more has been learned about myelodysplastic syndromes, they are considered to be a form of cancer.
A risk factor is something that increases the risk of developing a disease. It could be a behaviour, substance or condition. Most diseases are the result of many risk factors.
There is no known cause for myelodysplastic syndromes, but the following factors are linked with a higher risk of developing a myelodysplastic syndrome:
- exposure to high-dose radiation from an atomic bomb blast or a nuclear reactor accident
- certain geneticgeneticHaving to do with genes or genetics and usually referring to the effect or structure of genes. conditions such as Fanconi anemia, neurofibromatosis type 1 (von Recklinhausen disease), Shwachman-Diamond syndrome, Diamond-Blackfan anemia and dyskeratosis congenita
- long-term workplace exposure to benzene, petroleum products, fertilizers, pesticides or chemicals used in the rubber industry
- smoking cigarettes
Being treated for certain types of cancer can also increase your risk of developing a myelodysplastic syndrome. These include Hodgkin lymphoma, non-Hodgkin lymphoma (NHL), multiple myeloma, breast cancer, testicular cancer and childhood acute lymphocytic leukemia (ALL).
Having specific treatments can also increase the risk for a myelodysplastic syndrome, including:
- chemotherapy with certain drugs (only a small percentage of people who receive these drugs will develop a myelodysplastic syndrome)
- radiation therapy (the risk of developing a myelodysplastic syndrome is higher if both chemotherapy and radiation therapy were given)
- autologous stem cell transplant
A myelodysplastic syndrome may not cause any signs or symptoms in its early stages. Some people may have mild symptoms that slowly get worse over time.
The symptoms that develop depend on the type of blood cell that is most affected. Many people with a myelodysplastic syndrome have a low red blood cell count (called anemia). A low white blood cell count (called neutropenia), a low platelet count (called thrombocytopenia) or both can also mean you have a myelodysplastic syndrome.
Other health conditions can cause the same symptoms as a myelodysplastic syndrome. See your doctor if you have these symptoms:
- frequent infections
- easy bruising and bleeding
- shortness of breath
- a general feeling of discomfort or illness (called malaise)
- abdominal discomfort or a feeling of fullness if the spleen or liver is enlarged
Diagnosing a myelodysplastic syndrome usually begins with a trip to your family doctor or when a routine blood test suggests a problem with the blood. Your doctor will ask you about any symptoms you have and do a physical exam to check if your spleen or liver is enlarged. Based on this information, your doctor will order tests to check for a myelodysplastic syndrome or other health problems.
Some of the same tests used to rule out or diagnose leukemia are used to diagnose a myelodysplastic syndrome. These tests include:
- complete blood count (CBC) to measure the number and quality of white blood cells, red blood cells and platelets
- cytogenetic tests to look for certain changes to chromosomes in a sample of cells from the blood or bone marrow
- fluorescence in situ hybridization (FISH) to look for specific changes in chromosomes and some abnormalities that are too small for standard cytogenetic testing to find
- bone marrow aspiration and biopsy to find out if you have leukemia or a myelodysplastic syndrome
Find out more about these tests and procedures.
The World Health Organization (WHO) identifies the different types of myelodysplastic syndrome based on their cellular and clinical classifications.
Cellular classification is a way of identifying different types of myelodysplastic syndrome based on:
- how the blood and bone marrow cells look under a microscope
- the degree of dysplasiadysplasiaAbnormal development, appearance and organization of cells so that they are different from normal cells in size, shape and organization within tissue. Dysplasia almost always refers to a precancerous condition. in the blood and bone marrow cells
- chromosome changes in the blood and bone marrow cells
- how quickly the myelodysplastic syndrome is likely to develop into AML
Clinical classification is a way of identifying types of myelodysplastic syndrome based on what doctors believe is the main factor in the disease’s development. If doctors can’t identify the main cause, it is called primary myelodysplastic syndrome. If doctors think a previous cancer treatment caused the disease, it is called secondary myelodysplastic syndrome, or treatment-related myelodysplastic syndrome. Secondary myelodysplastic syndrome is more common than primary myelodysplastic syndrome.
Based on these classifications, doctors can identify the following types of myelodysplastic syndromes.
Refractory cytopenia with unilineage dysplasia (RCUD)
RCUD causes a low number of 1 type of blood cell. The counts for the other 2 types of blood cells are normal. The dysplasia is usually minimal.
- Refractory anemia (RA) means there is a low number of red blood cells in the blood.
- Refractory neutropenia (RN) means there is a low number of white blood cells in the blood.
- Refractory thrombocytopenia (RT) means there is a low number of platelets in the blood.
RCUD rarely develops into acute myelogenous leukemia (AML).
Refractory anemia with ring sideroblasts (RARS)
RARS means there is a low number of red blood cells in the blood. The counts for white blood cells and platelets are normal. At least 15% of the red blood cells have too much iron (called ring sideroblasts).
About 1%–2% of all cases of RARS develop into AML.
Refractory anemia with excess blasts (RAEB)
RAEB means there is a low number of red blood cells in the blood and there may also be a low number of white blood cells or platelets. The blood cells look abnormal in the bone marrow.
RAEB is divided into 2 categories based on the percentage of immature blood cells (called blasts) in the bone marrow.
RAEB-1 means 5%–9% of the cells in the bone marrow are blasts. About 25% of all cases of RAEB-1 develop into AML.
RAEB-2 means 10%–19% of the cells in the bone marrow are blasts. About 33% of all cases of RAEB-2 develop into AML.
Refractory cytopenia with multilineage dysplasia (RCMD)
RCMD means that there are low numbers of at least 2 types of blood cells (red blood cells, white blood cells or platelets) in the blood. If red blood cells are affected and they have too much iron, it is called RCMD-RS.
Both RCMD and RCMD-RS may develop into AML.
Unclassifiable myelodysplastic syndrome (MDS-U)
MDS-U means there is a low number of 1 type of blood cell (red blood cells, white blood cells or platelets) in the blood. The percentage of immature blood cells (called blasts) in the blood and bone marrow is normal.
This type of myelodysplastic syndrome is not common. Doctors make a diagnosis of MDS-U when the cells in the blood and bone marrow don’t fit any other type of myelodysplastic syndrome. The number of any type of blood cell in the blood may be lower than normal, but less than 10% of that type of blood cell looks abnormal in the bone marrow. The cells in the bone marrow have at least one chromosome abnormality that is only seen in myelodysplastic syndrome or leukemia.
Myelodysplastic syndrome associated with an isolated del[5q] chromosome abnormality
In this myelodysplastic syndrome, the number of red blood cells in the blood is low, the white blood cell count is normal and the platelet count is higher than normal. There is also a specific change in chromosome 5.
MDS associated with an isolated del[5q] chromosome abnormality rarely develops into AML.
People with a myelodysplastic syndrome may have questions about their prognosis and survival. Prognosis and survival depend on many factors. Only a doctor familiar with a person’s medical history, type of myelodysplastic syndrome, characteristics of the myelodysplastic syndrome, treatments chosen and response to treatment can put all of this information together to arrive at a prognosis.
Prognostic and predictive factors
A prognosis is the doctor’s best estimate of how a myelodysplastic syndrome will affect a person and how it will respond to treatment. A prognostic factor is an aspect of the myelodysplastic syndrome or a characteristic of the person that the doctor will consider when making a prognosis. A predictive factor influences how a myelodysplastic syndrome will respond to a certain treatment. Prognostic and predictive factors are often discussed together and they both play a part in deciding on a treatment plan and a prognosis.
The following are prognostic and predictive factors for myelodysplastic syndrome.
Type of MDS
Refractory cytopenia with unilineage dysplasia (RCUD) and refractory anemia with ring sideroblasts (RAEB) are least likely to develop into AML. They have a more favourable prognosis than other myelodysplastic syndromes.
Myelodysplastic syndrome associated with an isolated del[5q] chromosome rarely develops into AML and has a more favourable prognosis than other myelodysplastic syndromes.
Percentage of blasts in the bone marrow
A high percentage of blasts in the bone marrow points to a less favourable prognosis.
Low numbers of blood cells
Having low numbers of more than 1 type of blood cell (red blood cells, white blood cells or platelets) is a sign of a less favourable prognosis.
Changes to chromosome 7 usually mean a less favourable prognosis.
Simple changes mean that there are less than 3 changes to chromosomes. Simple changes are linked with a favourable prognosis.
Complex changes mean that there are more than 3 changes to chromosomes. Complex changes are linked with a less favourable prognosis.
Prognostic scoring systems
Doctors use the following prognostic scoring systems for myelodysplastic syndromes. Different factors are given a value and then a score. The total score is used to assign the myelodysplastic syndrome a risk category. A higher score suggests a greater chance that a myelodysplastic syndrome will develop into AML and a less favourable prognosis.
International Prognostic Scoring System (IPSS)
The IPSS rates 3 factors to predict the course of a myelodysplastic syndrome.
immature blood cells (called blast cells)
in the bone marrow
5% or less
chromosome changes (called cytogenetics)
normal (no change), del[5q] only or del[20q] only
all other changes not valued as good or poor
3 or more changes or abnormal chromosome 7
low blood cell counts
Each of the following counts has a value of 1:
0 or 1
2 or 3
The IPSS score is used to determine the risk category and the risk that the myelodysplastic syndrome will develop into AML in the next 5 years.
|Total score||IPSS risk||Risk of AML within|
2.5 or greater
World Health Organization (WHO) Prognostic Scoring System (WPSS)
The WPSS was developed more recently than the IPSS. It also uses 3 factors to predict the course of a myelodysplastic syndrome.
type of MDS
RCUD, RARS, del[5q]
good – one of the following:
intermediate – all other changes not valued as good or poor
poor – one of the following:
The WPSS points are used to determine the risk category and the risk that the myelodysplastic syndrome will develop into AML within 5 years.
|Total score||WPSS risk||Risk of AML within|
3 or 4
5 or 6
Your healthcare team will create a treatment plan just for you. The goal of treatment for myelodysplastic syndromes is to relieve symptoms, slow or stop the myelodysplastic syndrome from developing into AML and improve quality of life. You may be offered a combination of different treatments.
People with myelodysplastic syndromes may be treated with different drugs. For more information on certain drugs, go to sources of drug information.
Chemotherapy is the use of anticancer, or cytotoxic, drugs to destroy cancer cells. It may also be used to treat people with a myelodysplastic syndrome.
The most common chemotherapy drug used to treat myelodysplastic syndromes is cytarabine (Cytosar, Ara-C). Cytarabine may be combined with idarubicin (Idamycin).
Other chemotherapy drugs that may be used to treat myelodysplastic syndromes include:
- topotecan (Hycamtin)
- fludarabine (Fludara)
- daunorubucin (Cerubidine, daunomycin)
- mitoxantrone (Novantrone)
Other drugs that may be used to treat or prevent problems caused by low blood counts include:
- deferoxamine (Desferal)
- lenalidomide (Revlimid)
- antithymocyte globulin
- 5-azacytidine (Vidaza)
- decitabine (Dacogen)
People with low red blood cell counts (called anemia) may be given blood transfusions. Having blood transfusions can cause a buildup of extra iron, which is treated with medicines.
People with bleeding problems due to low platelet counts may be given platelet transfusions.
Growth factors are substances that regulate the growth, division and survival of cells. Not having enough healthy blood cells causes most of the symptoms of myelodysplastic syndromes. Growth factors help return blood cell counts to normal.
Epoetin alfa (Eprex, erythropoietin) helps improve the production of red blood cells.
Filgrastim (Neupogen) is a type of granulocyte colony-stimulating factor (G-CSF). It helps the bone marrow make white blood cells.
Stem cell transplant
A stem cell transplant may be a treatment option for some younger people or those with a high-risk myelodysplastic syndrome.
Follow-up after treatment is an important part of cancer care. Follow-up for myelodysplastic syndromes is often shared among the cancer specialists (oncologists) or blood specialists (hematologists) and your family doctor. Your healthcare team will work with you to decide on follow-up care to meet your needs.
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