According to the American Cancer Society, between 10,000 and 15,000 people in the United States are diagnosed each year with myelodysplastic syndrome (MDS). As the average age of the population in the U.S. goes up, the number of new cases seems to be increasing. Almost all people with MDS are more than 60 years old.
To better understand what happens to your blood when you have myelodysplastic syndrome, it helps to know what makes up normal blood and bone marrow.
There are three major types of blood cells: red blood cells (RBCs), white blood cells (WBCs) and platelets. These cells are made in the bone marrow and flow through the bloodstream in a liquid called plasma.
Red Blood Cells (RBCs), the major part of your blood, carry oxygen and carbon dioxide throughout your body. The percentage of RBCs in the blood is called hematocrit. The part of the RBC that carries oxygen is a protein called hemoglobin. All body tissues need oxygen to work properly. When the bone marrow is working normally, the RBC count remains stable. Anemia occurs when there are too few RBCs in the body. Symptoms of anemia include shortness of breath, weakness and fatigue.
White Blood Cells (WBCs) include several different types. Each has its own role in protecting the body from germs. The three major types are neutrophils, monocytes and lymphocytes.
- Neutrophils (also known as granulocytes or polys) destroy most bacteria.
- Monocytes destroy germs such as tuberculosis.
- Lymphocytes are responsible for destroying viruses and for overall management of the immune system. When lymphocytes see foreign material, they increase the body’s resistance to infection.
WBCs play a major role in fighting infection. Infections are more likely to occur when there are too few normal WBCs in the body.
Absolute Neutrophil Count (ANC) is a measure of the number of WBCs you have to fight infections. You can figure out your ANC by multiplying the total number of WBCs by the percentage of neutrophils (“neuts”). The K in the report means thousands. For example:
WBC = 1000 = 1.0K
Neuts = 50% (0.5)
1000 X 0.5 = 500 neutrophils
Also, when you receive your blood counts, this equation may be written as polys plus bands = neutrophils. Further, while anyone can catch a cold or other infections, this is more likely to occur when your ANC falls below 500. Your WBC count generally will fall within the first week you start chemotherapy, but it should be back to normal between 21 to 28 days after starting chemotherapy.
Platelets are the cells that help control bleeding. When you cut yourself, the platelets collect at the site of the injury and form a plug to stop the bleeding.
Bone Marrow is the soft tissue within the bones where blood cells are made. The bone marrow is made up of blood cells at different stages of maturity. All blood cells begin in the bone marrow as stem cells. Stem cells are very immature cells. When there is a need, the stem cells are signaled to develop into mature RBCs, WBCs or platelets. This signaling is done with “growth factors.”
As each cell fully matures, it is released from the bone marrow to circulate in the bloodstream. The blood circulating outside of the bone marrow in the heart, veins and arteries is called peripheral blood.
Myelodysplastic syndrome is a group of diseases in which the bone marrow doesn’t produce enough healthy blood cells, instead making too many immature cells (blasts). These blasts die in the marrow or soon after entering the bloodstream, resulting in too few healthy blood cells and low blood counts.
In its mildest form, MDS may be anemia, low platelets or low white blood count, but about 10% to 20% of diagnosed cases progress to acute myeloid leukemia (AML).
Myelodysplastic Syndrome Types
There are several types of MDS, and they are classified based on the number of abnormal cells in the blood and bone marrow. Types of myelodysplastic syndrome include:
- Refractory anemia
- Refractory cytopenia with multilineage dysplasia
- Refractory anemia with ringed sideroblasts
- Refractory cytopenia with multilineage dysplasia and ringed sideroblasts
- Refractory anemia with excess blasts
Myelodysplastic Syndrome Risk Factors
Anything that increases your chance of getting a disease is a risk factor. Most cases of myelodysplastic syndrome have no known cause, but some factors have been found to increase the risk.
Risk factors for myelodysplastic syndrome include:
- Age: MDS rarely occurs in people younger than 60
- Smoking tobacco
- Long-term exposure to chemicals, including benzene or other chemicals used in the petroleum and rubber industries
- Exposure to high levels of radiation, such a nuclear reactor accident or atomic bomb
- Prior chemotherapy or radiation therapy
- Inherited disorders, including:
- Fanconi anemia
- Shwachman-Diamond syndromes
- Familial platelet disorder
- Severe congenital neutropenia
Not everyone with risk factors gets MDS. However, if you have risk factors, it’s a good idea to discuss them with your health care provider.
Some cases of myelodysplastic syndrome can be passed down from one generation to the next. Genetic counseling may be right for you. Learn more about the risk to you and your family on our genetic testing page.