Mesalamine-Induced Eosinophilic Pneumonia

Eosinophilic pneumonia encompasses a group of lung disorders characterized by peripheral blood eosinophilia. While its etiology is often idiopathic or infectious, non-infectious causes, including drug-induced reactions, should also be considered. Common culprits of drug-induced eosinophilic pneumonia include daptomycin, phenytoin, and nitrofurantoin. Mesalamine-induced eosinophilic pneumonia is rare, with only a few cases documented in the literature. We present the case of a 27-year-old male patient who developed unilateral eosinophilic pneumonia following three months of mesalamine therapy for ulcerative colitis. Subsequent discontinuation of mesalamine led to rapid resolution of his symptoms, supporting a diagnosis of mesalamine-induced eosinophilic pneumonia.