FMS-like Tyrosine Kinase-3 Mutation in a Child with Standard-risk ALL and Normal Karyotype

FMS-like tyrosine kinase-3 is a receptor tyrosine kinase expressed by immature hematopoietic cells and is important for the normal development of stem cells and immune system. Mutations of FMS-like tyrosine kinase-3 have been detected in about 30% of patients with acute myelogenous leukemia and a small number of patients with acute lymphoblastic leukemia. The FMS-like tyrosine kinase-3 mutations most often involve small tandem duplications of amino acids within the juxtamembrane domain of the receptor and are called internal tandem duplications. The other type of mutations in FMS-like tyrosine kinase-3 is located in the activation loop of the second tyrosine kinase domain. Multiple studies have shown that activating mutations of FMS-like tyrosine kinase-3 are common in blasts from patients with acute myeloid leukemia but are rarely found in adult patients with acute lymphoblastic leukemia. In addition, activating FLT3 mutations occur only rarely in T-ALL cases. Here we report a 3-year-old girl with acute lymphoblastic leukemia who had a mutation in FMS-like tyrosine kinase-3 / internal tandem duplications.