Leukemia Facts

April 19, 2024 
This page was reviewed under our medical and editorial policy by Guido Marcucci, M.D., Chair, Department of Hematologic Malignancies Translational Science, City of Hope Duarte

Leukemia accounts for about 3% of all new U.S. cancer cases. This type of blood cancer is the 10th most common cancer in the United States, and it's the most common cancer affecting teens and children.

What Is Leukemia?

Leukemia is a type of cancer involving blood cells. This disease develops in tissues where blood forms, such as bone marrow.

Bone marrow generates the cells that eventually develop into platelets, red blood cells and white blood cells. Typically, healthy cells form in the bone marrow and mature into red blood cells — delivering oxygen and nutrients to the body’s tissues — white blood cells fight infections and platelets stop bleeding.

In patients with leukemia, these cells do not mature as they should, or they transform into irregular blood cells that do not function normally. As abnormal cells build up in the bone marrow and bloodstream, the patient may experience anemia, susceptibility to infections and bleeding that does not clot due to the lack of functional red blood cells, white blood cells and platelets.

What Causes Leukemia?

Leukemia develops when certain genetic changes occur in the bone marrow, leading to mutations that cause cells to react abnormally.

The damaged blood cells then grow and divide uncontrollably, eventually crowding out healthy cells. When the damaged cells build up in the system, the patient experiences an imbalance in the proportion of healthy blood cells, which may then lead to leukemia symptoms.

Leukemia Risk Factors

Factors that may put patients at higher risk for developing leukemia are called risk factors.

Researchers do not yet fully understand what causes most cases of leukemia, but some factors that may increase the risk for developing leukemia are listed below.

• History: A personal or family history of leukemia, another type of blood cancer or other blood disorders may increase a person's risk for developing leukemia.
• Previous cancer therapies: Prior treatment with radiation therapy or chemotherapy are believed to raise a person's leukemia risk.
• Chemicals: Exposure to radiation or certain chemicals, including benzene, formaldehyde and Agent Orange, are known leukemia risk factors.
• Certain genetic factors: Genetic conditions such as Down syndrome, blood syndrome, Li-Fraumeni syndrome or Fanconi anemia may raise the risk for developing leukemia.
• Previous conditions: Infections with specific viruses, such as the Epstein-Barr virus or human T cell lymphoma/leukemia virus (HTLV-1), are believed to lead to an increased leukemia risk.
• Gender: Leukemia is more commonly diagnosed in males than females.
• Smoking: Tobacco smoking raises the risk for developing certain types of leukemia.
• Age: Overall, leukemia most commonly affects people over the age of 60, but in the subtype of acute lymphocytic leukemia, most people diagnosed with the disease are between 2 and 5 years of age.

Having a certain risk factor does not mean you'll develop leukemia, and not everyone with this disease has one of the risk factors listed above. In most cases, the care team is unable to pinpoint specifically what causes someone's leukemia.

Hereditary Causes of Leukemia

In some cases, children inherit DNA mutations from a parent, increasing their risk for cancer. Certain inherited conditions can heighten the risk for developing childhood leukemia, but most childhood leukemias do not appear to result from inherited mutations. Usually, DNA mutations related to leukemia develop after conception. However, some of these acquired mutations might occur early, even before birth.