The bone marrow is the principal source of the many different types of cells that circulate in your blood stream. The term “myelodysplasia“ describes certain abnormalities in the production of these blood cells. “Myelodysplastic syndrome” (MDS) refer to at least five different entities, all of which interfere with the growth of blood cells in the bone marrow. The differences among them are found in the appearance of the cells under the microscope and are helpful primarily in determining prognosis.
MDS frequently progresses to a form of acute leukemia. Leukemia is a cancer of the blood cells. But in the case of leukemia, there is an overproduction of immature cells (blasts) circulating in the blood and an underproduction of healthy cells. In MDS, there is usually, but not always, only an underproduction of healthy cells. The progression to acute leukemia is so common that MDS used to be known as “preleukemia.”
The bone marrow contains stem cells, which have the capacity to become any of the cell types that circulate in the blood stream. These stem cells normally undergo a maturation process that results in mature cells with fixed functions:
Once cells have matured in the bone marrow, they are released into the blood circulation. MDS interrupts the normal maturation process of blood cells.
Roughly 3,000 new cases of MDS occur yearly in the United States. A similar rate of 1 to 10 per 100,000 people occurs in the rest of the developed nations. Cases without a known cause are most frequently found in older males, usually between 70 and 80 years of age; among this group, the rate rises to 25 per 100,000 people.
The incidence of MDS among younger populations is rising. This is partially due to the success of chemotherapy and radiation in treating and eradicating other forms of cancer since these therapies increase the risk of developing MDS.
The exact cause of MDS is unclear, but certain factors are believed to increase risk. These include radiation for the treatment of cancer, certain drugs and chemicals, genetic factors, and some birth defects.
MDS may lead to a number of complications related to blood cells:
Bleeding —If blood clotting elements (like platelets) become depleted, bleeding may become uncontrollable.
Infection —If immune cells (white blood cells) are depleted, even small infections can be serious.
Anemia —When the number of red blood cells decreases, anemia may develop. A lack of red blood cells reduces the oxygen-carrying capacity of the blood and may cause fatigue, shortness of breath, palpitations.
Leukemia —MDS commonly leads to acute leukemia.
Castro-Malaspina H, O’Reilly RJ. Aplastic anemia and the myelodysplastic syndromes. In: Harrison's Principles of Internal Medicine. 14th ed. McGraw-Hill; 1998.
Silverman LR. Myelodysplastic syndrome. In: Cancer Medicine. American Cancer Society website. Available at: http://www.nci.nih.gov/cancer_information/ . Accessed November 30, 2002.
Last reviewed December 2014 by Mohei Abouzied, MD, FACP
Last Updated: 12/20/2014