Pediatric Hypereosinophilia: Characteristics, Clinical Manifestations, and Diagnoses

Eosinophilia is associated with various conditions, including allergic, infectious, and neoplastic disorders. The diagnostic differential is broad, and data on hypereosinophilia in pediatric patients are limited. The objectives of this study were to identify cases of hypereosinophilia in a tertiary pediatric medical center, determine clinical characteristics and disease associations, and estimate the incidence of hypereosinophilia in the hospital and geographic populations. A retrospective chart review included patients younger than 18 years presenting to a tertiary pediatric medical center (January 1, 2008, to May 31, 2017) with absolute eosinophil counts (AECs) greater than or equal to 1.50 thousand eosinophils/microliter (K/μL) recorded on at least 2 occasions at least 4 weeks apart (N = 176). Clinical characteristics, laboratory values, treatment course, and associated diagnoses were evaluated. The most common cause of hypereosinophilia in this cohort was secondary hypereosinophilia. Atopic dermatitis, graft-versus-host disease, sickle cell disease, and parasitic infections were the most common conditions associated with hypereosinophilia. Median age at diagnosis was 4.6 (interquartile range, 1.5-10.5) years. Median peak AEC was 3.16 (2.46-4.78) K/μL. Hypereosinophilia occurred most frequently in patients aged between 6 and 11 years (24.4%) and younger than 1 year (18.2%). Patients with neoplasms and immune deficiencies had significantly higher peak AECs than did patients with overlap hypereosinophilic syndrome and atopic diseases (P < .0001). Pediatric hypereosinophilia has an incidence of 54.4 per 100,000 persons per year, with children younger than 1 year and aged 6 to 11 years accounting for most affected patients. Pediatric hypereosinophilia is not uncommon and remains underrecognized, highlighting a need for clinicians to identify patients who meet criteria for hypereosinophilia and to pursue a thorough evaluation.