Idiopathic Hypereosinophilic Syndrome Diagnosed in an Infant: A Case Report

ABSTRACT

Introduction: Idiopathic hypereosinophilic syndrome (IHES) is a rare disorder characterized by persistent eosinophilia (>1.5 x 109/L) for >=6 months, tissue infiltration with end-organ damage, and exclusion of known causes for hypereosinophilia. It is mainly observed in adults, and rarely in children. We report, to our knowledge, the first case report of IHES in an infant. Case Description A 5-month-old male presented with severe failure to thrive and malnutrition. His hospitalization was complicated by acute kidney injury, pulmonary edema requiring intubation, pseudomonas bacteremia with concomitant tibial osteomyelitis, COVID-19 infection, and bradycardic arrest requiring CPR. Notably, patient had persistent eosinophilia (maximum 11.4 x 109/L) (Table 1). Parasite testing was negative. Immune work-up was normal (Table 1). Primary immunodeficiency panel testing of 407 geneswas negative. Endoscopy revealed eosinophilia in the sigmoid colon and rectum. Bone marrow biopsy revealed a low normocellular bone marrow (70%) with maturing trilineage hematopoiesis and increased eosinophils and eosinophil precursors (approximately 50% of nucleated cells). A FISH panel was negative for PDGRFRA/4q12, PDGRFRB/5q33, FGFR1/8p12, and ETV6/12p13 gene regions. The patient was diagnosed with IHES and started on steroids at 0.5 mg/kg/day. Hydroxyurea was added due to up-trending eosinophil count despite steroid therapy. Three months post-diagnosis, he is doing well off medications, with most recent eosinophil count being 2.1 x 109/L. Discussion(s) Hypereosinophilia in children is most commonly due to secondary causes such as atopic dermatitis, parasitic infections, neoplasms, graft-versus-host disease, sickle cell disease, and immunodeficiency. Once the above diagnoses have been excluded, IHES should be considered, especially in patients with evidence of end-organ damage. Copyright © 2022