Anatomy of the bone. The bone is made up of compact bone, spongy bone, and bone marrow. Compact bone makes up the outer layer of the bone. Spongy bone is found mostly at the ends of bones and contains red marrow. Bone marrow is found in the center of most bones and has many blood vessels. There are two types of bone marrow: red and yellow. Red marrow contains blood stem cells that can become red blood cells, white blood cells, or platelets. Yellow marrow is made mostly of fat.
A blood stem cell may become a lymphoid stem cell or a myeloid stem cell. A lymphoid stem cell becomes a white blood 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.
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. These 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.
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.
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.
Signs and symptoms of a myelodysplastic syndrome include shortness of breath and feeling tired.
Myelodysplastic syndromes often do not cause early signs or symptoms. They may be found during a routine blood test. Signs and symptoms may be caused by myelodysplastic syndromes or by other conditions. Check with your doctor if you have any of the following:
- 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.
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.
- Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances, such as vitamin B12 and folate, released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
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.
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 following tests may be done on the sample of tissue that is removed:
- Immunocytochemistry: A test that uses antibodies to check for certain antigens in a sample of bone marrow. This type of test is used to tell the difference between myelodysplastic syndromes, leukemia, and other conditions.
- Immunophenotyping: A process used to identify cells, based on the types of antigens or markers on the surface of the cell. This process is used to diagnose specific types of leukemia and other blood disorders by comparing the cancer cells to normal cells of the immune system.
- Flow cytometry: A laboratory test that measures the number of cells in a sample, the percentage of live cells in a sample, and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light.
- FISH (fluorescence in situ hybridization): A laboratory technique used to look at genes or chromosomes in cells and tissues. Pieces of DNA that contain a fluorescent dye are made in the laboratory and added to cells or tissues on a glass slide. When these pieces of DNA bind to specific genes or areas of chromosomes on the slide, they light up when viewed under a microscope with a special light.
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 signs or 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.