Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 21 2 2022 04 11 215 218 EN Jie Hee Jue Department of Pediatrics, Keimyung University School of Medicine, Keimyung University Dongsan Hospital, Daegu, Korea Ye Jee Shim Department of Pediatrics, Keimyung University School of Medicine, Keimyung University Dongsan Hospital, Daegu, Korea Sunggyun Park Department of Laboratory Medicine, Keimyung University School of Medicine, Keimyung University Dongsan Hospital, Daegu, Korea Do-Hoon Kim Department of Laboratory Medicine, Keimyung University School of Medicine, Keimyung University Dongsan Hospital, Daegu, Korea Hye Ra Jung Department of Pathology, Keimyung University School of Medicine, Keimyung University Dongsan Hospital, Daegu, Korea 2021 04 29 2021 09 23 A four-year-old female patient visited the pediatric hematologic clinic due to periodic generalized edema and eosinophilia. Laboratory assessment showed an eosinophil count of 40.02×109/L (73.6% of white blood cells). A bone marrow aspirate smear film showed no signs of malignant cells but had hypercellular marrow particles with eosinophilia (45% of all nucleated cells) and 52% of eosinophils were immature. Other laboratory tests showed an increased IgM level of 827 mg/dL, and lymphocyte phenotyping by flow cytometry revealed an aberrant CD3−CD4+ T-cell population of 27–53×109/L (1.9–3.6% of lymphocytes). Polymerase chain reaction analysis for the T-cell receptor gamma gene rearrangement showed a T-cell clonality peak. At the age of 13, allogeneic stem cell transplantation was performed, but with primary rejection. From the age of 17, she has continued receiving 3 mg/kg of reslizumab intravenously every 4 weeks for 21 months. Since reslizumab treatment was initiated, her eosinophil count remained consistently within the normal range. This is the first report describing the effective use of reslizumab in a Korean adolescent patient for the management of lymphocytic-variant hypereosinophilic syndrome (L-HES). Since the patient showed clinical manifestations of L-HES as well as episodic angioedema with eosinophilia (EAE), a continuous periodic examination is required given the higher risk of developing lymphoma or leukemia. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3216 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3216/1833