Introduction. FLT3 is a tyrosine kinase receptor involved in the proliferation and differentiation of hematopoietic stem cells. There are two types of common FLT3 gene mutation, internal tandem duplication and the D835 mutation, which are known to be associated with a poor clinical outcome in acute leukemia patients. Methods. This study evaluates the incidence of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) in 38 pediatric patients diagnosed with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) in Hospital Universiti Sains Malaysia. DNA extraction was done from archive bone marrow samples to determine FLT3-ITD mutations using polymerase chain reaction. Results. In this pediatric series, the age ranges were 2–14 years. However, no FLT3-ITD mutations were detected in any of the samples. Conclusion. This preliminary study suggested that the incidence of FLT3 gene mutation most probably was very low in pediatrics patients diagnosed with acute leukemia. A further study with larger number of patient samples is necessary to confirm the findings and to further appreciate the prognostic value of FLT3-ITD mutation among pediatrics patients. 1. Introduction Fms-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase expressed by immature hematopoietic cells. FLT3 ligand is expressed by marrow stromal cells and other cells and synergizes with other growth factors to stimulate proliferation and differentiation of stem cells, progenitor cells, dendritic cells, and natural killer cells. In normal hematopoietic cells, FLT3-ITDs (internal tandem duplications) mutations have not been detected in the cord blood and bone marrow [1–5]. In general, there are 2 types of FLT3 mutations which are internal tandem duplications (FLT3/ITD mutations) in or near the juxtamembrane domain of the receptor and point mutations resulting in single amino acid substitutions occurring within the activation loop of the tyrosine kinase domain (FLT3/TKD mutations). Both mutations are known to be associated with a poor clinical outcome in acute leukemia patients. The incidence of FLT3/ITD mutations varies according to age and clinical risk group, being less common in pediatric acute myeloid leukemia (AML) and in AML arising from an antecedent myelodysplastic syndrome. FLT3 mutations are genetic changes that have been reported to have prognostic significance in acute myeloid leukemia (AML) [6]. Study by Thiede et al. in 2002 analyzed the prevalence of FLT3-ITD mutations in 979 AML patients, with 20.4% found to be positive. However, the tandem duplication
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