Abstract
Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by pruritic, scaly, erythematous lesions, xerosis, and lichenification. Dupilumab, a monoclonal antibody targeting I‐ (IL)‐4 and IL‐13 signaling, is widely used to treat moderate to severe AD. We report a 22 year‐old male with a history of asthma and chronic childhood AD who was started on dupilumab 300 mg every 2 weeks after multiple relapses despite topical therapy. Baseline Eczema Area and Severity Index (EASI), Dermatology Life Quality Index (DLQI), and Physician Global Assessment (PGA) scores were not recorded; however, the patient showed marked clinical improvement of his skin disease, with a posttreatment EASI score of 1. Five months after dupilumab initiation, he presented with palpitations and pleuritic chest pain. His absolute eosinophil count was 2070 cells/μL, increased from a pretreatment baseline of 860 cells/μL, with an elevated Troponin I of 1.56 ng/mL. Electrocardiography showed normal sinus rhythm. Cardiac magnetic resonance demonstrated myocardial edema, early gadolinium enhancement, and late gadolinium enhancement involving the interventricular septum and adjacent walls, confirming myocarditis. A comprehensive workup, including antinuclear antibody, antineutrophil cytoplasmic antibody, renal function, a respiratory viral PCR panel, stool ova and parasites, and whole exome sequencing, excluded autoimmune, infectious, and familial causes. Computed tomography of the sinuses demonstrated moderate rhinosinusitis without invasive features. A diagnosis of eosinophilic myocarditis secondary to dupilumab‐associated hypereosinophilia was made. Dupilumab was discontinued, and the patient was treated with corticosteroids and colchicine, with resolution of eosinophilia and symptoms. Although dupilumab‐associated eosinophilia is usually mild and transient, this case highlights the importance of maintaining a high index of suspicion for rare but serious organ involvement, particularly in patients with new cardiopulmonary symptoms or baseline eosinophilia, while recognizing that routine eosinophil monitoring is not currently recommended for all patients receiving dupilumab.