Hypereosinophilic syndrome: A report of two cases and review of the literature

Abstract

Introduction: Hypereosinophilic syndrome (HES) is a rare condition that is estimated to affect 1 out of every 1 to 2 per million people in the United States of America. HES is a heterogeneous group of disorders characterized by persistent eosinophilia with systemic organ dysfunction related either to eosinophilic infiltration or eosinophil-associated tissue damage. Case Report: We describe two female patients who presented with eosinophilia and hepato-splenomegaly and were diagnosed with HES. Both patients were negative for mutations in PDGFR-α but their presentations were otherwise consistent with the myeloproliferative variant of HES. Both patients were responsive to steroid therapy, but adverse effects necessitated discontinuation in one. Discussion: The pathophysiology of HES is based on endothelial damage with subsequent fibrosis, leading to infarction and thrombosis as a result of the release of eosinophil derived toxins from cells sequestered in organ systems. Criteria for the diagnosis of HES include eosinophil count of greater than 1.5x109/L, which persists beyond 6 months, and evidence of end-organ damage. Underlying causes such as parasitosis, allergy and drug reactions must be excluded. The PDGFR-α mutation is reportedly found in 17-56 % of cases of HES and was negative in both cases presented in this report. Imatinib therapy is recommended for patients with the PDGFR-α mutations who are usually steroid resistant.
Conclusion: HES is a rare disorder with serious potential for multi-system pathology. The accurate identification of the variant facilitates targeted therapy where this is applicable. Thefavorable outcome in the reported cases is likely related to the absence of neurologic and cardio-pulmonary involvement.