Persistent Hemorrhagic Lip Crusts as the Presenting Sign of Pediatric <i>FIP1L1</i> – <i>PDGFRA</i> ‐Positive Hypereosinophilic Syndrome: A Case Report and Review of the Literature

FIP1-like-1-platelet-derived growth factor receptor-α (FIP1L1-PDGFRA)-positive hypereosinophilic syndrome (HES) is a rare myeloproliferative neoplasm characterized by persistent eosinophilia and occurs predominantly in middle-aged adults. We report a 15-year-old boy with FIP1L1-PDGFRA-associated chronic eosinophilic leukemia who initially presented with persistent hemorrhagic crusts on the lower lip, an uncommon mucocutaneous manifestation resulting from thrombotic aggregates of eosinophil granule proteins. This case is followed by a systematic literature review of pediatric FIP1L1-PDGFRA-positive HES to further characterize its clinical features and outcomes in children.