FIP1L1-PDGFRA-Positive Chronic Eosinophilic Leukemia: A Low-Burden Disease with Dramatic Response to Imatinib - A Report of 5 Cases from South India.

OBJECTIVE: Eosinophilia associated with FIP1L1-PDGFRA rearrangement represents a subset of chronic eosinophilic leukemia and affected patients are sensitive to imatinib treatment. This study was undertaken to learn the prevalence and associated clinicopathologic and genetic features of FIP1L1-PDGFRA rearrangement in a cohort of 26 adult patients presenting with profound eosinophilia (>1.5x10(9)/L). MATERIALS AND METHODS: Reverse-transcriptase polymerase chain reaction and gel electrophoresis were used for the detection of FIP1L1-PDGFRA rearrangement. RESULTS: Five male patients with splenomegaly carried the FIP1L1-PDGFRA gene rearrangement. All patients achieved complete hematological response within 4 weeks of starting imatinib. One patient had previous deep vein thrombosis and 1 patient had cardiomyopathy, which improved with steroids and imatinib. Conventional cytogenetics was normal in all these patients. No primary resistance to imatinib was noted. CONCLUSION: This study indicates the need to do the FIP1L1-PDGFRA assay in patients with hypereosinophilic syndrome. Prompt treatment of this condition with imatinib can lead to complete hematological response and resolution of the organ damage that can be seen in this setting.