Risk factors for acute lymphoblastic leukemia (ALL)

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes acute lymphoblastic leukemia (ALL) develops in people who don’t have any of the risk factors described below.

Men develop ALL a little more often than women.

Some people with certain genetic conditions have a higher than average risk for ALL. Talk to your doctor about your risk. If you have a genetic condition that increases the risk of ALL, you may need to visit your doctor more often to check for ALL. Your doctor will recommend what tests you should have and how often you should have them.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.

Risk factors

Genetic syndromes



Radiation therapy

There is convincing evidence that the following factors increase your risk for ALL.

Genetic syndromes

Genetic syndromes are groups of symptoms caused by a change, or mutation, in one or more genes. They are passed from parents to children. Having certain genetic syndromes can increase the risk of ALL, especially childhood ALL. The following genetic syndromes increase the risk for ALL. Other genetic syndromes may also increase the risk of ALL.

Down syndrome is a condition caused by an extra (third) copy of chromosome 21. It causes different birth defects, intellectual disability, a characteristic facial appearance and poor muscle tone in infancy. People with Down syndrome have a higher risk of developing several medical conditions, including childhood leukemia.

Bloom syndrome is a condition caused by a large number of abnormal chromosomes. People with Bloom syndrome are usually smaller than average and have a high-pitched voice and a characteristic facial appearance. People with Bloom syndrome have a higher risk of developing different types of cancer, including ALL.

Ataxia-telangiectasia (AT) is a rare condition that affects the nervous system, immune system and other body systems. People with AT have problems with walking, balance and coordination. They often have a weakened immune system and a higher risk of developing cancer, particularly lymphoma and leukemia.

Li-Fraumeni syndrome is a rare condition that greatly increases the risk of developing several types of cancer, including breast cancer, osteosarcoma, soft tissue sarcomas, brain cancer and leukemia.

Neurofibromatosis type 1 (von Recklinghausen disease) is a condition in which tumours that start in nerve tissue form in the skin, just under the skin and in cranial and spinal cord nerves. People with neurofibromatosis type 1 have a higher risk of developing certain cancers, including leukemia.

Other conditions like Klinefelter syndrome and Fanconi anemia increase the risk of acute myelogenous leukemia (AML) but it is not clear if they also increase the risk of ALL.

High levels of radiation

Coming into contact with high levels of radiation is a risk factor of ALL. For example, people coming into contact with radiation from nuclear reactor accidents have a higher risk of ALL. But most leukemias that develop after exposure to radiation are AML rather than ALL.


Infection with the human T-cell leukemia/lymphoma virus, type 1 (HTLV-1) increases the risk of developing a rare type of T-cell ALL. In many cases, people carrying the virus do not get symptoms or develop health problems from it. Only a few people who have HTLV-1 will develop leukemia. HTLV-1 is not common in Canada. It is more common in Japan and the Caribbean.

Previous radiation therapy

Radiation therapy given to treat cancer or other health conditions increases the risk of leukemia. The leukemia that develops is usually acute myelogenous leukemia (AML). But some studies have shown that radiation can also increase the risk of ALL.

Possible risk factors

The following factors have been linked with ALL, but there is not enough evidence to show for sure that they are risk factors. More research is needed to clarify the role of these factors for ALL.

  • previous chemotherapy
  • aoverweight or obesity

Questions to ask your healthcare team

To make the decisions that are right for you, ask your healthcare team questions about risks.

Expert review and references

Reducing your risk for acute lymphoblastic leukemia (ALL)

You may lower your risk of developing acute lymphoblastic leukemia (ALL) by keeping a healthy body weight.

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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