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A risk factor is something that increases your chance of getting a disease such as cancer. Some risk factors, like smoking, can be controlled. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even several risk factors, does not mean that you will definitely get the disease. And many people who get the disease may have few or no known risk factors.

There are only a handful of known risk factors for acute lymphocytic leukemia (ALL).

Radiation exposure

Being exposed to high levels of radiation is a risk factor for both ALL and acute myeloid leukemia (AML). For example, Japanese atomic bomb survivors had a greatly increased risk of developing acute leukemia.

Treating cancer with radiation therapy also increases the risk of leukemia, although more for AML than ALL. The risk seems to be higher if chemotherapy and radiation are both used in treatment.

The possible risks of leukemia from being exposed to lower levels of radiation, such as from medical imaging tests like x-rays or CT scans, are not well understood. Exposure to such radiation, especially very early in life, may carry an increased risk of leukemia, but this is not clear. If there is an increased risk it is likely to be small, but to be safe, most doctors try to limit radiation exposure from these tests as much as possible, especially in children and pregnant women.

Certain chemical exposures

The risk of ALL may be increased by exposure to certain chemotherapy drugs and certain other chemicals, including benzene. Benzene is used in many industries to make other products, and is also in cigarette smoke, as well as some glues, cleaning products, detergents, art supplies, and paint strippers.

Chemical exposure is more strongly linked to an increased risk of AML than to ALL.

Certain viral infections

Infection with the human T-cell lymphoma/leukemia virus-1 (HTLV-1) can cause a rare type of T-cell ALL. Most cases occur in Japan and the Caribbean area. This disease is not common in the United States.

In Africa, the Epstein-Barr virus (EBV) has been linked to Burkitt lymphoma, as well as to a form of ALL. In the United States, EBV most often causes infectious mononucleosis (“mono”).It has also been linked with a type of lymphoma that can occur after a stem cell transplant (known as post-transplant lymphoproliferative disorder, or PTLD).

Certain genetic syndromes

ALL itself doesn't appear to have a strong inherited component. That is, it doesn't seem to run in families, so a person’s risk is not increased if a family member (other than an identical twin - see below) has the disease.

But there are some genetic syndromes (some of which can be inherited from a parent) that seem to raise the risk of ALL. These include:

• Down syndrome
• Klinefelter syndrome
• Fanconi anemia
• Bloom syndrome
• Ataxia-telangiectasia
• Neurofibromatosis
• Li-Fraumeni syndrome

Age

ALL is more likely to occur in children and in adults over the age of 50.

Race/ethnicity

ALL is more common in White individuals than in African Americans, but the reasons for this are not clear.

Being male

In general, l?eukemia is more common in men than women. This includes ALL that is more common in males than in females. The reason for this is not clear.

Having an identical twin with ALL

Someone who has an identical twin who develops ALL in the first year of life has an increased risk of getting ALL.

Uncertain, unproven or controversial risk factors

Other factors that have been studied for a possible link to ALL include:

• Exposure to electromagnetic fields (such as living near power lines or using cell phones)
• Workplace exposure to diesel, gasoline, pesticides, and certain other chemicals
• Smoking
• Exposure to hair dyes

So far, none of these factors has been linked conclusively to ALL, but research in these areas continues.