Leukemia

Leukemia is cancer of the white blood cells. These cells normally help your body fight infection. Most blood cells form in the bone marrow. In leukemia, cancerous blood cells form and crowd out the healthy blood cells in the bone marrow, making it hard for blood to do its work.

The type of leukemia depends on the type of blood cell that has become cancerous. Common types of leukemia include:

• acute lymphocytic leukemia
• acute myeloid leukemia
• chronic lymphocytic leukemia
• chronic myeloid leukemia

Lymphocytic leukemias are cancers of the lymphoblasts and myeloid leukemias are cancers of the granulocytes. Lymphoblasts and granulocytes are both types of white blood cells that fight infection as part of your natural immune system.

Leukemia is either acute or chronic. Acute leukemia is a fast-growing cancer that usually gets worse quickly. Chronic leukemia is a slower-growing cancer that gets worse slowly over time.

Leukemia occurs most often in adults older than 55 years, and it is the most common cancer in children younger than 15 years. Adults can get either acute or chronic leukemia; children with leukemia most often have an acute type.

The treatment and prognosis for leukemia depend on the type of blood cell affected and whether the leukemia is acute or chronic. Some leukemias can be cured. Other types are hard to cure, but you can often control them. Chemotherapy is often used to treat leukemia. Radiation therapy and stem cell transplantation may also be used.

It is not clear what causes leukemia. In general, cancer occurs when your blood cells develop errors (mutations) in their DNA. The errors make cells grow and divide out of control. The accumulating abnormal cells crowd out healthy cells and prevent the blood from working the way it is supposed to work.

Risk factors for developing leukemia include:

• previous cancer treatment. Certain types of chemotherapy and radiation therapy for other cancers can increase your risk of developing certain types of leukemia.
• genetic disorders. Genetic abnormalities may play a role in the development of leukemia. Certain genetic disorders, such as Down syndrome, are also associated with an increased risk of leukemia.
• exposure to certain chemicals. Exposure to certain chemicals, such as benzene — which is found in gasoline and is used by the chemical industry — is also linked to an increased risk of some kinds of leukemia.
• smoking. Smoking cigarettes increases the risk of acute myelogenous leukemia.
• family history of leukemia. If members of your family have been diagnosed with leukemia, your risk for the disease may be increased.

See your doctor for persistent fatigue, frequent infections, easy bleeding or bruising, swollen lymph nodes, or unexplained weight loss. Blood tests can detect leukemia, and early diagnosis improves treatment.