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Cancer In Depth: Myelodysplastic Syndrome (MDS)

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) refers to at least 5 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.

Stem Cells

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:

  • Red blood cells carry oxygen.
  • 3 types of granulocytes (a type of white blood cell) carry out immune functions.
  • 2 types of lymphocytes (a type of white blood cell) carry out immune functions.
  • Macrophages and monocytes help us fight infection.
  • Platelets provide a defense against bleeding and bruising.

Once cells have matured in the bone marrow, they are released into the blood circulation. MDS interrupts the normal maturation process of blood cells.

Causes and Complications

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, and palpitations.

Leukemia—MDS commonly leads to acute leukemia.

Revision Information

  • Castro-Malaspina H, O’Reilly RJ. Aplastic anemia and the myelodysplastic syndromes. In: Harrison's Principles of Internal Medicine. 14th ed. McGraw-Hill; 1998.

  • General information about myelodysplastic syndromes. National Cancer Institute website. Available at: Updated August 12, 2015. Accessed December 7, 2015.

  • Myelodysplastic syndrome. EBSCO DynaMed website. Available at: Updated November 7, 2014. Accessed December 7, 2015.