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Acute lymphoblastic leukemia (ALL) is a malignant disorder of lymphoid progenitor cells, affecting both children and adults. The disease peaks between the ages of 2-5years with an incidence of 3-4/100,000 in patients between 0-14 years and 1/100,000 in those over 15 years. ALL is believed to originate from genetic aberrations in blood progenitor cells that will differentiate into T-cells or B-cells. The events leading up to the development of ALL are largely unknown, however some environmental and genetic factors have been linked. Less than 5% appear to be associated with inherited genetic syndromes. Environmental factors such as exposure to ionizing radiation and/or chemotherapeutic drugs in utero, pesticides and solvents appear to increase the risk of leukemia.
ALL can be divided into several categories according to phenotype. B-ALL (BCP-ALL) is a malignancy of lymphoblasts that are of B-cell lineage which is the main disease seen in children. T-ALL is seen in approximately 15% of children and 25% of adults. ALL can be further classified using the FAB classification representing cytomorphological features (L1-L3) and also immunophenotypic features which are the expression of cell specific antigens.
ALL has a good prognosis for pediatric patients with overall survival of 80%. Unfortunately, adult sufferers have a high remission rate but lower overall survival of 40-50%. Age, leucocyte count, ethnicity, weight and genetic factors play a role in risk stratifying patients. Treatment usually consists of remission-induction phase, intensification phase and continuation therapy, with an additional focus on the central nervous system to prevent relapse.