Hypereosinophilic syndrome (HES) is a rare, heterogeneous disorder, characterised by high eosinophil levels (≥1500 cells/µL) and eosinophilic inflammation leading to multiorgan dysfunction and damage[1,2]. Dermatological, respiratory, gastrointestinal and/or cardiovascular manifestations are frequently reported in patients with HES[1]. Treatment goals are long-term reduction of blood and tissue eosinophil counts to halt progression and prevent further eosinophil-mediated organ damage[2,3]. Mepolizumab, a first-in-class humanised monoclonal antibody, specifically targets interleukin-5, thereby inhibiting eosinophil production, activation and survival[4].
