Myelodysplastic syndromes are a group of diseases in which the bone marrow does not make enough healthy blood cells.
Myelodysplastic syndromes are diseases of the blood and bone marrow. Normally, the bone marrow makes blood stem cells (immature cells) that develop into mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. The lymphoid stem cell develops into a white blood cell. The myeloid stem cell develops into one of three types of mature blood cells:
- Red blood cells that carry oxygen and other materials to all tissues of the body.
- White blood cells that fight infection and disease.
- Platelets that help prevent bleeding by causing blood clots to form.
Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
In myelodysplastic syndromes, the blood stem cells do not mature into healthy red blood cells, white blood cells, or platelets. The immature blood cells, called blasts, do not function normally and either die in the bone marrow or soon after they enter the blood. This leaves less room for healthy white blood cells, red blood cells, and platelets to develop in the bone marrow. When there are fewer blood cells, infection, anemia, or easy bleeding may occur.
There are several types of myelodysplastic syndromes.
Myelodysplastic syndromes have too few of one or more types of healthy blood cells in the bone marrow or blood. Myelodysplastic syndromes include the following diseases:
- Refractory anemia.
- Refractory anemia with ringed sideroblasts.
- Refractory anemia with excess blasts.
- Refractory anemia with excess blasts in transformation.
- Refractory cytopenia with multilineage dysplasia.
- Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality.
- Unclassifiable myelodysplastic syndrome.
See the following PDQ summaries for information about other blood cell diseases:
- Myelodysplastic/ Myeloproliferative Neoplasms Treatment
- Chronic Myeloproliferative Disorders Treatment
Age and past treatment with chemotherapy or radiation therapy affect the risk of developing a myelodysplastic syndrome.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get a disease; not having risk factors doesn't mean that you will not get a disease. People who think they may be at risk should discuss this with their doctor. Risk factors for myelodysplastic syndromes include the following:
- Being male or white.
- Being older than 60 years.
- Past treatment with chemotherapy or radiation therapy.
- Being exposed to certain chemicals, including tobacco smoke, pesticides, and solvents such as benzene.
- Being exposed to heavy metals, such as mercury or lead.
Possible signs of myelodysplastic syndrome include feeling tired and shortness of breath.
Myelodysplastic syndromes often do not cause early symptoms and are sometimes found during a routine blood test. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
- Shortness of breath.
- Weakness or feeling tired.
- Having skin that is paler than usual.
- Easy bruising or bleeding.
- Petechiae (flat, pinpoint spots under the skin caused by bleeding).
- Fever or frequent infections.