Risk Factors
ALL in Children. In 2005, experts estimated that about 3,970 cases of acute lymphocytic leukemia would be diagnosed in the US, with about 2,670 of them in children and adolescents younger than age 20. Until recently, most studies listed it as the most common childhood cancer. (Some recent evidence suggests that cancers in the central nervous system may be surpassing ALL in children.) The disease typically develops in children ages 1 to 10 years old, but the disease can strike from infancy to old age.
ALL in Adults. About 30% of ALL cases occur in adults. Adults who develop ALL are usually male and over 50 years old, with the highest risk being above age 70.
Ethnicity and ALL
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Caucasian and Asian children have a much higher risk for ALL than African-American children, although African-American and Hispanic children who develop it do not appear to fare as well. Socioeconomic factors and inequal access to healthcare may account for some of these differences.
Hereditary Disorders
Certain inherited disorders can increase the risk for leukemia. For example, children with Down's syndrome have a 20-fold greater risk of developing acute leukemia than the general population. Other rare genetic disorders associated with increased risk include Bloom syndrome, Fanconi's anemia, ataxia-telangiectasia, neurofibromatosis, Schwachman syndrome, IgA deficiency, and congenital X-linked agammaglobulinemia.
People Exposed to Radiation
Children treated with radiation and chemotherapy for Hodgkin's disease are at higher risk for acute leukemia within 2 to 13 years after treatment (usually of the myeloid variety). Children under 10 are most susceptible to acute leukemia following exposure to radiation treatments. Susceptibility decreases between the ages of 10 and 19 then increases slowly again through age 50. After 50, a person is again at high risk of developing acute leukemia following ionizing radiation.
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