Leukemia is cancer of the body's blood-forming tissues, including the bone marrow and lymph system. When this condition occurs, bone marrow produces a large number of abnormal white blood cells — or, in some cases, a large number of red blood cells or platelets.
Normal white blood cells are potent infection fighters. But in people with leukemia, abnormal white blood cells tend to accumulate, blocking production of normal white blood cells and impairing the ability to fight infection.
Treatment for leukemia is complex. Most patients are treated with chemotherapy. Some also may have radiation therapy, a blood or marrow transplant (BMT) or biological therapy.
Many people believe leukemia only affects children, but roughly 10 times as many adults as children are diagnosed with this cancer. New cases of leukemia number nearly 30,000 annually in the United States.
There are six main types of leukemia:
All types of leukemia are treatable and some are potentially curable.
Leukemia is grouped by how quickly it develops, as well as the type of blood cells it affects. The different forms of leukemia vary greatly in their nature and seriousness and they are classified as either "acute" or "chronic."
Leukemias also are classified as "myeloid" or "lymphoid." This refers to the type of white blood cell that has become cancerous. Myeloid cells give rise to neutrophils, an important type of white blood cell that kills bacteria, as well as red blood cells (which deliver oxygen to the tissues) and platelets (which help clot the blood). Lymphoid cells give rise to lymphocytes, which protect against bacterial germs, including viruses.