Risk Factors

Risk factors, further detailed in subsequent chapters, are a part of the epidemiology of ALL, both with regard to initial factors leading to ALL and factors associated with success or failure of treatment. ALL may occur at any age, but is most frequent in childhood (before age 15), with a consistent incidence in the third to eighth decades of life.46 In adults, family history and a history of immunologic abnormalities are usually not present. Family history of lymphoma may be present without a definite association being drawn.27,40

Risk factors for ALL include Caucasian race as compared to African-American or other ethnic groups in the United States. Rates of ALL are also higher in Northern and Western Europe, North America, and Oceania versus in Asian and black populations.40 In Israel, Jews have a higher incidence of leukemias, but paradoxically lower rates of ALL.46

Exposure to human T-cell leukemia virus 1 may produce a T-cell leukemia presenting with hypercalcemia, bone or skin lesions, lymph node enlargement, which occur in several ethnic populations, such as Japanese from the island of Kyushu and U.S. immigrants from the Caribbean. An initial, more indolent T-cell leukemia may evolve to a very aggressive T-ALL that is treated with great difficulty and responds poorly, with little chance of survival.44 ALL can also occur as a blastic transformation of CML, and in this setting it is always associated with a t(9;22).

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