Mesalazine-associated lung fibrosis: case report and literature review

Even though uncommon, drug-induced interstitial lung disease (DIILD) represents a serious adverse drug reaction. We report a case of a patient with a history of ulcerative colitis who was receiving mesalazine.

The patient developed dyspnea, hypoxemia, and respiratory failure accompanied by resting oxygen desaturation. Initial CT imaging revealed bilateral perihilar ground-glass opacities along with focal areas of consolidation. Inflammatory markers were elevated, but procalcitonin levels remained persistently low; sputum cultures and multiplex PCR ruled against an infectious origin. Mesalazine was discontinued, and the patient's respiratory status improved dramatically. Follow-up CT revealed interval resolution of the pulmonary lesions, and a diagnosis of DIILD was clinically established.

This case emphasizes the importance of balancing clinical suspicion between steroid-related infectious risk and an uncommon drug reaction. We also identified similar Mesalazine-associated DIILD cases in the literature to demonstrate similar radiologic patterns, onset time, and outcomes.