Idiopathic Hypereosinophilia: A Multicenter Retrospective Analysis

PURPOSE: Physicians can sometimes encounter idiopathic hypereosinophilia (HE), but little is known about it. In this multicenter study, we analyzed the clinical characteristics, treatment, and outcomes of patients with idiopathic HE. PATIENTS AND METHODS: Patients diagnosed with idiopathic HE (idiopathic hypereosinophilic syndrome: iHES or hypereosinophilia with undetermined significance: HEus) at six tertiary hospitals between January 2010 and June 2021 were included in this retrospective observational study. Demographics, clinical and laboratory data, and treatment responses were obtained from the electronic medical records of the study subjects. RESULTS: A total of 73 patients with idiopathic HE (45 with iHES and 28 with HEus) were included in the present study. Overall, 12 (26.7%) and 5 (17.9%) were women, and mean age of patients at diagnosis was 51.84 ± 17.29 years and 60.21 ± 18.01 years in iHES and HEus groups, respectively. Forty-three (95.6%) patients of iHES and 15 (53.6%) patients of HEus received corticosteroids as 1st-line treatment. Treatment response to corticosteroids in patients with iHES was generally good: complete response (n=25, 58.1%), partial response (n=12, 27.9%), no response (n=6, 14.0%). Treatment response to corticosteroids in HEus was complete response (n=7, 46.7%), partial response (n=6, 40.0%), and no response (n=2, 13.3%). There were 13 patients (46.4%) with HEus who were not treated. CONCLUSION: Corticosteroid treatment is generally effective and well tolerated by patients with iHES. Some patients with HEus are treated with corticosteroids in clinical practice. Extensive research is needed to establish a standardized management guidelines for iHES and determine whether treatment for HEus is required.