Successful Treatment of Relapsing Chronic Eosinophilic Pneumonia With Mepolizumab: A Case Report

We present a case of a 73-year-old male with a five-month history of progressive dyspnea on exertion, cough, and worsening hypoxemia. Initial lab work did not identify peripheral eosinophilia. Chest computed tomography identified extensive ground-glass opacities in the mid-basilar. Diagnostic bronchoscopy showed an eosinophilic-rich bronchoalveolar lavage representing 63% of the total white blood cell count, confirming the diagnosis of chronic eosinophilic pneumonia. No etiology was identified despite extensive diagnostic workup. Our patient had a prolonged course of prednisone taper treatment complicated by frequent hospitalizations, osteopenia, and insomnia. Additionally, his chronic eosinophilic pneumonia relapsed shortly after stopping steroids. In our patient, off-label treatment with mepolizumab, an interleukin-5-inhibiting monoclonal antibody, was associated with symptomatic relief, imaging findings resolution, and remission maintenance without systemic steroids.