Pb2172: prevalence of fip1l1-pdgfrα fusion in tunisian patients with hypereosinophilia

Topic: 15. Myeloproliferative neoplasms - Biology & Translational Research Background: Hypereosinophilia (HE) is a heterogeneous disorder defined by a persistent high count of eosinophils, which can be seen in a variety of conditions with distinct pathophysiological pathways. HE may be associated with tissue or organ damage, and, in this case, the disorder is classified as hypereosinophilic syndrome (HES). Remarkable progress has been achieved to improve diagnosis, including the finding of a cryptic interstitial deletion on chromosome 4q12 resulting in a FIP1L1-PDGFRa fusion gene which predicts a favorable response to Tyrosine kinase Inhibitors (TKI). Aims: The aim of this study is to evaluate the prevalence of FIP1L1-PDGFRα fusion gene in patients with hypereosinophilia and to describe the epidemiological and clinical characteristics of the cohort. Methods: A retrospective descriptive observational study including all patients referred to the hematology laboratory of Pasteur Institute of Tunis over a 5-year period from January 2018 to December 2022. Included patients presented persistent eosinophilia superior to 0.5G/L. FIP1L1-PDGFRα rearrangement testing was performed on peripheral blood collected on EDTA, using nested RT-PCR. Demographic data, and biological parameters were collected. Results: 202 patients were included, the mean age was 48 years [4 months –95 years] with a sex ratio M/F= 1.17. 80.2% of patients had isolated hypereosinophilia, 19.8 % had additional organ damages. The most affected organs were digestive (21%), dermatological (10.7%) multisystemic (7.1%) venous thrombosis (7%),cardiovascular (3.6%) and pulmonary (3.6%). Mean leucocytes count was 20.9 G/L [4.9-101.7], Mean eosinophilic count was 7.8 G/L [8-87]. 18.4% of patients had mild hypereosinophilia [0.5-1.5],43.2% had moderate hypereosinophilia [1.5-5] and 38.4% severe hypereosinophilia >=5G/L. FIP1L1-PDGFRA fusion gene was found in 8 patients, all males. The mean age of positive patients was 46.7 [25-77]. 80% FIP1L1-PDGFRα positive patients had severe hypereosinophilia. FIP1L1-PDGFRα positive patients were treated with imatinib 100mg/day with good response, 1 patient experienced disease relapse within 4 years, 1 patient has beneficed from treatment free remission after 5 years. Summary/Conclusion: The FIP1L1-PDGFRα rearrangement is rare among patients with hypereosinophilia, additional novel treatment options should be tested to improve the quality of life of patients. Keywords: FIP1L1-PDGFRA, Eosinophilia, Hypereosinophilic syndrome