Leukemia is a cancer of the blood cells. Leukemia begins when normal blood cells change and grow uncontrollably. Blood cells (including red cells that carry oxygen, white cells that fight infection, and platelets that cause blood to clot) are produced in the bone marrow, which is the spongy tissue inside the larger bones in the body. Abnormalities in the bone marrow cells can cause the overproduction or underproduction of certain blood cells. There are four main types of leukemia in adults:
Eosinophilia is a condition that develops when the bone marrow makes too many eosinophils, a type of white blood cell that is involved in allergic reactions or used to fight certain parasites.
Chronic eosinophilic leukemia is a subtype of clonal (from an acquired genetic abnormality) eosinophilia that is sometimes called hypereosinophilic syndrome (HES). This disease is classified as a myeloproliferative disorder (myelo- refers to bone marrow, proliferative means excess).
People can also have high numbers of 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). For more information, read the guide to Acute Myeloid Leukemia.
Statistics
Eosinophilic leukemia is rare; no specific statistics are available.
Find out more about basic cancer terms used in this section.
Last Updated: September 15, 2009
