Leukemia is a cancer that forms in the tissue that makes blood. In a person that has leukemia, the bone marrow makes abnormal white blood cells which are called leukemia cells. They crowd the normal cells, red blood cells, white blood cells, and platelets, and keep those cells from doing what they are supposed to do.
There are two main types of leukemia:
Each of these two types of leukemia can further be divided into two classifications - acute and chronic:
Acute means the abnormal cells are immature, they multiply quickly, and so the disease becomes worse faster. The large numbers don’t leave room for the healthy cells, so the person develops anemia from a low red cell count, cannot fight infection because of the low white cell count, and bruises and bleeds easily because of the low platelet count.
Chronic means there are fewer immature blast cells and more mature abnormal cells. They multiply slower that the others and function normally for a time. Eventually there are too many abnormal white cells and anemia forms as well as a decreased immune response.
See leukemia in Webster's New World College Dictionary
Origin: ModL: see leuco- & -emia
See leukemia in American Heritage Dictionary 4
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