Pediatric Acute Myeloid Leukemia

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Acute leukemias are clonal diseases characterized by a maturation arrest and by enhanced proliferation of hematopoietic precursor cells, which normally would differentiate into mature blood cells. The leukemic cells are released from the bone marrow into the peripheral blood and may accumulate in vital organs such as the spleen, liver, skin, central nervous system and lymph nodes. Chronic leukemias arise form hyperproliferation without a clear maturation arrest. In children, chronic leukemias are rare, and most cases are classified as acute leukemias. (Pui, et al 2011) Acute leukemias can be further subdivided in acute lymphoblastic leukemias (ALL, either from precursor Tor B-cells), and in acute myeloid leukemias (AML, either from red blood cell precursors, platelet precursors, or granulocytic or monocytic precursors). In children, approximately 80% of cases are ALL, and 15-20% AML. There is a peak in the incidence of AML in infants under one year of age, after which the incidence is low throughout childhood. (Creutzig, et al 2010a, Kaspers and Zwaan 2007) AML may even be present in newborn babies. (Bresters, et al 2002) In adolescents the incidence of AML starts to rise and rises further throughout adult life (1-3 per 105 each year in childhood, rising to 15 per 105 in early adulthood to 35 per 105 at the age of 90 years). (Ries, et al 1999) AML may either arise de novo or occur following underlying diseases such as myelodysplastic syndrome, which is much more frequent in elderly patients with AML than in children. Other underlying diseases may be chromosomal-breakage syndromes such as Fanconi anemia. (Tonnies, et al 2003) Moreover, AML may be secondary to previous exposure to irradiation or to chemotherapy, including both alkylating chemotherapy and epipodopyllotoxins. (Sandler, et al 1997, Weiss, et al 2003) A specific type of AML arises in children with Down syndrome. (Zwaan, et al 2008) Exposure to environmental factors has also been described as a potential cause of AML. (Smith, et al 2011) Infrequently, families with an unexplained high risk of AML have been described which suggests that germ-line mutations such as RUNX1 and CEBPA may play a role in leukemogenesis. (Owen, et al 2008)