Clonal eosinophilia with exclusive pulmonary involvement driven by PDGFRA rearrangement treated with imatinib: A case report.

Hypereosinophilic syndrome (HES) was first described in 1968 by Hardy and Anderson. It is a group of rare, multisystemic and heterogeneous pathologies, characterized by significant morbidity and mortality. The occurrence of clonal hypereosinophilic syndrome associated with FIP 1L1-PDGFRA+ is estimated to range between 0.31 and 6.3 cases per million individuals. The organs most commonly impacted are the heart and spleen, with the lungs being the next most affected. Clonal hypereosinophilic syndromes with exclusive pulmonary involvement are exceptional. Due to the rarity of clonal HES, this report aims to not only describe the patient's clinical, biological, and radiological manifestations of clonal HES but also enrich the literature to ameliorate the management of this uncommon syndrome. we report the case of a patient with past medical history of obstructive bronchopneumopathy who was presented with cough and dyspnea. Investigations revealed peripheral blood hypereosinophilia (between 4000 and 9000/mm3) which lead us to suspect clonal hypereosinophilic syndrome (HES). This diagnosis was confirmed by cytogenetics/fluorescence in situ hybridization (FISH) which demonstrated a positive FIP 1L1-PDGFRA rearrangement. The CTAP confirmed isolated lung involvement with interstitial infiltrate of the subpleural territories of both lung bases and the bronchoalveolar lavage showed eosinophil count elevated at 15%. The patient was treated by imatinib at a dose of 100 mg/day was initiated. The patient follow-up showed a reduction in eosinophils count to 7500/mm3 at two months of treatment. A molecular evaluation is scheduled in 3 months to assess the response to imatinib.