A myelodysplastic syndrome is a disease in which the bone marrow does not make enough healthy blood cells.

A myelodysplastic syndrome is a group of symptoms that includes cancer of the blood and bone marrow. In a healthy person, the bone marrow makes blood stem cells (immature cells) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. A myeloid stem cell becomes one of three types of mature blood cells:

• Red blood cells that carry oxygen and other substances to all tissues of the body.
• Platelets that form blood clots to stop bleeding.
• White blood cells that fight infection and disease.

A lymphoid stem cell becomes a white blood cell.

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Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.

In a patient with a myelodysplastic syndrome, the blood stem cells (immature cells) do not become healthy red blood cells, white blood cells, or platelets. The immature blood cells, called blasts, do not work the way they should and either die in the bone marrow or soon after they go into the blood. This leaves less room for healthy white blood cells, red blood cells, and platelets to form in the bone marrow. When there are fewer healthy blood cells, infection, anemia, or easy bleeding may occur.

Age and past treatment with chemotherapy or radiation therapy affect the risk of 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. Talk with your doctor if you think you may be at risk. Risk factors for myelodysplastic syndromes include the following:

• Past treatment with chemotherapy or radiation therapy for cancer.
• Being exposed to certain chemicals, including tobacco smoke, pesticides, fertilizers, and solvents such as benzene.
• Being exposed to heavy metals, such as mercury or lead.

The cause of myelodysplastic syndromes in most patients is not known.

Possible signs of a 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. Check with your doctor if you have any of the following problems:

• 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).

Tests that examine the blood and bone marrow are used to detect (find) and diagnose myelodysplastic syndromes.

The following tests and procedures may be used:

• Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.

• Complete blood count (CBC) with differential : A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the blood sample made up of red blood cells.
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  Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.

• Peripheral blood smear : A procedure in which a sample of blood is checked for changes in the number, type, shape, and size of blood cells and for too much iron in the red blood cells.

• Cytogenetic analysis : A test in which cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes.

• Bone marrow aspiration and biopsy : The removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for abnormal cells.
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  Bone marrow aspiration and biopsy. After a small area of skin is numbed, a Jamshidi needle (a long, hollow needle) is inserted into the patient’s hip bone. Samples of blood, bone, and bone marrow are removed for examination under a microscope.

The different types of myelodysplastic syndromes are diagnosed based on certain changes in the blood cells and bone marrow.

• Refractory anemia: There are too few red blood cells in the blood and the patient has anemia. The number of white blood cells and platelets is normal.

• Refractory anemia with ring sideroblasts: There are too few red blood cells in the blood and the patient has anemia. The red blood cells have too much iron inside the cell. The number of white blood cells and platelets is normal.

• Refractory anemia with excess blasts: There are too few red blood cells in the blood and the patient has anemia. Five percent to 19% of the cells in the bone marrow are blasts. There also may be changes to the white blood cells and platelets. Refractory anemia with excess blasts may progress to acute myeloid leukemia (AML). See the PDQ Adult Acute Myeloid Leukemia Treatment summary for more information.

• Refractory cytopenia with multilineage dysplasia: There are too few of at least two types of blood cells (red blood cells, platelets, or white blood cells). Less than 5% of the cells in the bone marrow are blasts and less than 1% of the cells in the blood are blasts. If red blood cells are affected, they may have extra iron. Refractory cytopenia may progress to acute myeloid leukemia (AML).

• Refractory cytopenia with unilineage dysplasia: There are too few of one type of blood cell (red blood cells, platelets, or white blood cells). There are changes in 10% or more of two other types of blood cells. Less than 5% of the cells in the bone marrow are blasts and less than 1% of the cells in the blood are blasts.

• Unclassifiable myelodysplastic syndrome: The numbers of blasts in the bone marrow and blood are normal, and the disease is not one of the other myelodysplastic syndromes.

• Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality: There are too few red blood cells in the blood and the patient has anemia. Less than 5% of the cells in the bone marrow and blood are blasts. There is a specific change in the chromosome.

• Chronic myelomonocytic leukemia (CMML): See the PDQ summary on Myelodysplastic/ Myeloproliferative Neoplasms Treatment for more information.

See the PDQ summary on Chronic Myeloproliferative Disorders Treatment for information about other blood cell diseases.

Certain factors affect prognosis and treatment options.

The prognosis (chance of recovery) and treatment options depend on the following:

• The number of blast cells in the bone marrow.
• Whether one or more types of blood cells are affected.
• Whether the patient has symptoms of anemia, bleeding, or infection.
• Whether the patient has a low or high risk of leukemia.
• Certain changes in the chromosomes.
• Whether the myelodysplastic syndrome occurred after chemotherapy or radiation therapy for cancer.
• The age and general health of the patient.