ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: In idiopathic hypereosinophilic syndrome (Cools et al, 2003), there is another parallel to the CML experience in that acquired drug resistance was observed in one patient with emergence of a point mutation in PDGFRA-FIP1L1, again showing structural analogy to the T315I mutation of BCR-ABL.