Ricker Polsdorfer, MD and Michael Jubinville, MPH
MDS refers to a group of disorders that affect the bone marrow's ability to produce normal, healthy blood cells. This leads to problems with the immune system, oxygen delivery, and blood clotting.
All blood cells start as stem cells that are formed in the bone marrow. Stem cells can mature into a variety of different blood cell types that have specific functions in the body. These include:
New, healthy cells are developed in the bone marrow to replace old or damaged cells. This ensures there is a consistent number of blood cells in the body. With MDS, there is an excessive amount of stem cells that do not fully mature. The immature stem cells crowd the bone marrow making it difficult for new, healthy cells to develop. Overcrowding also pushes immature blood cells into the bloodstream too early. Immature blood cells are not fully formed enough to be functional. The lower levels of healthy cells lead to a weakened immune system, problems problems with oxygen delivery, or problems controlling bleeding depending on the type of blood cells that are affected.
The instruction for cell growth and cell death exists in the DNA of each cell. Primary MDS is the result of damage to DNA. The damage may be the result of genetics, environmental factors like radiation exposure, changes related to age, or a combination of these factors.
Secondary MDS is associated with a history of cancer treatment. Chemo- and radiation therapy can damage the bone marrow and how it functions.
The World Health Organization (WHO) identifies several types of MDS. Each type has certain characteristics based on how bone marrow or blood cells look under a microscope. They include:
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Last reviewed December 2015 by Mohei Abouzied, MD
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