FLT3 mutations found in the juxtamembrane region and activation loop in ALL and AML. (A) An alignment of the juxtamembrane regions encompassing amino acids 563-610 of FLT3 and 544-589 of c-KIT is shown. The region of mutation of c-KIT in GIST is in bold as are the 4 FLT3 mutations found in ALL samples 12, 24, 21, and 25. (B) The different FLT3 mutations found in AML and ALL are shown. Internal tandem duplications (FLT3-ITDs) in the juxtamembrane region have been described in AML.^2,3  Two FLT3-ITDs are shown as examples. Deletions in the juxtamembrane region are found in ALL. Activation loop mutations are found in ALL, AML, and MLL.^4,6