Work

Late‐Onset Mesalazine‐Induced Eosinophilic Pneumonitis Presenting as Non‐Resolving Pneumonia: A Diagnostic Pitfall in Ulcerative Colitis

Year: 2026

Type: article

Abstract: Mesalazine is widely used in the management of ulcerative colitis and is generally well tolerated. Rarely, it can cause eosinophilic pneumonitis, a potentially serious form of drug-induced lung injury that often mimics infection. We report a 24-year-old male with longstanding ulcerative colitis on mesalazine therapy for 2 years and 4 months who presented with progressive dyspnea and non-resolving pulmonary infiltrates. Despite empirical antibiotic therapy, his respiratory symptoms worsened. Investigations revealed marked peripheral eosinophilia and bilateral subpleural ground-glass opacities on CT imaging. Mesalazine-induced eosinophilic pneumonitis was suspected. Drug withdrawal and systemic corticosteroid therapy resulted in rapid clinical and radiological improvement. This case highlights that mesalazine-related pulmonary toxicity may occur even after prolonged stable therapy and should be considered in patients with ulcerative colitis presenting with unexplained or non-resolving respiratory symptoms.

Source: Clinical Case Reports

DOI: 10.1002/ccr3.72029

Authors: Siraj Nasim, Tamer Mohamed Zaalouk, Abu Bocus, Maged Kerols

Institution: Queen Elizabeth the Queen Mother Hospital

Language: English

Topic: Interstitial Lung Diseases and Idiopathic Pulmonary Fibrosis

Subfield: Pulmonary and Respiratory Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $1,820