Leukemia is a cancer of the blood cells. Leukemia begins when normal blood cells change and grow uncontrollably. Blood cells are produced in the bone marrow, the spongy tissue inside the larger bones in the body. There are different types of blood cells, including red blood cells that carry oxygen throughout the body, white cells that fight infection, and platelets that help the blood to clot. Abnormalities (changes) in the bone marrow cells can cause too many or too few of certain blood cells. There are four main types of leukemia in adults:
About eosinophilic leukemia
Eosinophilia is a condition that develops when the bone marrow makes too many eosinophils, a type of white blood cell involved in allergic reactions or used to fight certain parasites.
Chronic eosinophilic leukemia is a subtype of clonal eosinophilia, meaning it is caused by a new genetic change. It is sometimes called hypereosinophilic syndrome (HES). This disease is classified as a myeloproliferative disorder (myelo- means bone marrow and proliferative means too much).
People can also have many eosinophils without having cancer. For example, sometimes the body makes too many eosinophils in response to an allergen or a parasite. This type of eosinophilia is called secondary eosinophilia and is much more common than eosinophilic leukemia.
This section focuses on chronic eosinophilic leukemia. Acute eosinophilic leukemia is rare and is treated similarly to acute myeloid leukemia (AML).
Find out more about basic cancer terms used in this section.
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Last Updated: June 16, 2011
