Oral Lichenoid Reactions Caused by Mesalazine for Treatment of Ulcerative Colitis: A Case Report and Review of the Literature.

Background: Mesalazine, also known as 5-aminosalicylic acid (5-ASA), is commonly used to treat ulcerative colitis and Crohn's disease. While various adverse effects of mesalazine have been reported, oral lichenoid reactions (OLRs) are rarely associated with its use. Objective: The aim of this study is to present a rare case of mesalazine-induced OLR and a brief review of the relevant literature. Case Presentation: A 45-year-old female with ulcerative colitis, treated with mesalazine for 2 years, presented with persistent roughness and burning sensation on the bilateral buccal mucosa for 6 months. Clinical examination revealed well-demarcated, bilateral white striations. Patient refused any type of biopsy, but after ruling out other potential causes, mesalazine was discontinued, resulting in complete symptom resolution and near-total disappearance of oral lesions within 1 month, suggesting the diagnosis. Methods: A literature review was conducted using PubMed, Scopus, and Cochrane Library databases to identify similar cases and relevant information on mesalazine-induced OLRs. Results: This case represents one of the few documented instances of mesalazine-induced lichenoid reactions and a rare report of such involvement exclusively in the oral cavity, distinguishing it from previously reported cases, which involved concurrent cutaneous lesions. Conclusion: This report highlights the importance of considering mesalazine as a potential etiological factor in patients presenting with oral lichenoid lesions, particularly those with inflammatory bowel disease. It underscores the need for increased awareness among clinicians to facilitate the timely recognition and management of similar cases.