FIP1L1/PDGFRA fusion gene, del(4q12)
The FIP1L1/PDGFRA fusion gene is the result of an interstitial deletion of about 800 kb in 4q12, including CHIC2 locus, del(4)(q12q12). This translocation is not detected with classical cytogenetic techniques and has been identified in 50 – 60% of patients with hypereosinophilic syndrome (HES). Deletion of CHIC2 in patients with idiopathic hypereosinophilic syndrome (HES) and chronic eosinophilic leukaemia (CEL) results in the fusion of FIP1L1 with PDGFRA producing a tyrosine kinase which transforms haematopoietic cells. The discovery of the fusion gene FIP1L1/PDGFRA in cytogenetically normal patients with systemic mastocytosis with eosinophilia or idiopathic hypereosinophilic syndrome has redefined these diseases as clonal eosinophilia.
Detection of this fusion gene in patients with idiopathic hypereosinophilic syndrome (HES) or chronic eosinophilic leukaemia (CEL) can therefore lead to therapeutic choices based in the use of imatinib mesylate (Gleevec).
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