The exact cause of acute lymphocytic leukemia (ALL) has not been identified. Researchers, however, have gained a greater understanding of how specific changes in DNA can cause bone marrow stem cells to develop into leukemia.

Some forms of cancer are caused by DNA mutations that “turn on” oncogenes (genes that speed up cell division) or “turn off” tumor suppressor genes (genes that slow down cell division or cause cells to die at the right time). In people with leukemia, these mutations are normally acquired after birth. The mutations may occur from exposure to radiation or cancer-causing chemicals, but many times the mutations occur for no apparent reason.

One form of DNA abnormality that can cause leukemia to develop is a translocation. A translocation is the transfer of DNA from one chromosome to another. This abnormality can turn on oncogenes which causes rapid cell division. The translocation that is most commonly seen in people with ALL is the Philadelphia chromosome. Named after the city in which it was discovered, this translocation occurs between chromosomes 9 and 22 and occurs in about 20 to 25 percent of cases of ALL. Although they occur less often, deletions (the loss of part of a chromosome) and inversions (the rearrangement of DNA in part of a chromosome) also can cause ALL to develop.

In addition, researchers have identified a number of factors that increase a person’s chances of developing ALL. These risk factors include:

• Exposure to high levels of radiation. Patients who have received radiation therapy as treatment for other forms of cancer have an increased risk of developing ALL later in life. In addition, people exposed to radiation from atomic blasts (such as those in Japan during World War II) and nuclear accidents have an increased risk of developing the disease. Many researchers  have investigated the relationship of power lines and leukemia. They have not been able to definitively prove that electromagnetic field (EMF) exposure increases the risk of cancer. Most studies have indicated that there is either very little or no risk from exposure to EMF.
  
  
• Chemotherapy. Patients treated with certain chemotherapy drugs are at an increased risk of developing leukemia later in life. This risk may be greater with those individuals who have received higher-than-standard chemotherapy treatments.
  
  
• Human T-cell lymphoma/leukemia virus (HTLV-I). Infection with this virus can cause a rare type of ALL. The virus occurs most often in Japan and the Caribbean and is not common in the United States.
  
  
• Burkitt lymphoma. A form of lymphoma (cancer of the lymphoid tissue), Burkitt lymphoma can form a type of ALL. It has been linked to infection with the Epstein-Barr virus (the virus that causes mononucleosis) and is more common in Africa.
  
  
• Down syndrome and other specific genetic diseases. Patients with certain diseases caused by abnormal chromosomes may have an increased risk of developing ALL.
  
  
• Race. White people have a higher risk of developing the disease than African Americans.
  
  
• Age. The disease most often occurs in young children, typically between the ages of 3 and 6. The risk of developing ALL is lowest for people between the ages of 25 and 50. After age 50, the risk begins to increase.  According to the American Cancer Society (ACS), a 30-year-old person’s chance of developing ALL is 1 in 200,000. For a 70 year old person, the odds are 1 in 80,000.
  
  
• Gender. The disease is slightly more common in males than in females.

Although acute lymphocytic leukemia is associated with these risk factors, most patients with the disease have no known risk factors.