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What Is Leukemia?

Leukemia is usually thought of as a children’s condition, but it actually affects more adults. It’s more common in men than women, and more in Caucasians than African-Americans.

There’s really nothing you can do to prevent leukemia. It’s cancer of your blood cells caused by a rise in the number of white blood cells in your body. They crowd out the red blood cells and platelets your body needs to be healthy. All those extra white blood cells don’t work right, and that causes problems.

How Does It Happen?

Blood has three types of cells: white blood cells that fight infection, red blood cells that carry oxygen, and platelets that help blood to clot.

Every day, billions of new blood cells are produced in the bone marrow -- most of them red cells. But when you have leukemia, your body makes more white cells than it needs.

There are two main types of white blood cells in your body: lymphoid cells and myeloid cells. Leukemia can happen in either type.

These leukemia cells can’t fight infection the way normal white blood cells do. And because there are so many of them, they start to affect the way your major organs function. Eventually, there aren’t enough red blood cells to supply oxygen, enough platelets to clot the blood, or enough normal white blood cells to fight infection.

Along with infection, this can cause problems like anemia, bruising, and bleeding.

Types of Leukemia

Leukemia is grouped in two ways:

  1. Based on how fast it develops and gets worse
  2. Based on which type of blood cell is involved (usually myeloid or lymphoid)

These types are then put into one of two categories: acute or chronic.

  1. Acute leukemia happens when most of the abnormal blood cells stay immature and can’t carry out normal functions. It can get bad very fast.
  2. Chronic leukemia happens when there are some immature cells, but others are normal and can function normally. That means it gets bad, but more slowly.


No one knows exactly what causes leukemia. People who have it have certain abnormal chromosomes, but the chromosomes don’t cause the leukemia.

You can’t really prevent leukemia, but it may be possible that certain things in your environment could trigger the development of it. For example, if you are a tobacco smoker, you are more prone to some types of leukemia than a non-smoker. It’s also associated with a high amount of radiation exposure, and certain chemicals.

Some kinds of chemotherapy and radiation therapy used to treat other cancers can actually cause leukemia. The chance that you’ll develop leukemia depends on the types of chemotherapy drugs used.

Family history is another risk factor for leukemia. For example, if an identical twin gets a certain type of leukemia, there is a 20% chance the other twin will have it within a year.

WebMD Medical Reference Reviewed by William Blahd, MD on September 06, 2016



American Cancer Society: "Learn About Cancer (Detailed Guide): Leukemia -- Acute Lymphocitic."

American Cancer Society: "Learn About Cancer: Leukemia -- Acute Myeloid (AML)."

American Cancer Society: "Learn About Cancer: Leukemia -- Chronic Lymphocytic (CLL)."

American Cancer Society: "Learn About Cancer: Leukemia -- Chronic Myeloid (CML)."

American Cancer Society: "Learn About Cancer: Leukemia in Children."

National Cancer Institute: "Leukemia."

Leukemia & Lymphoma Society: "Leukemia."

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