Dear Editor: Mesalamine is a medication used widely in the treatment of patients with inflammatory bowel disease. Although mesalamine is considered safe, hepatotoxicity has been reported with an incidence of 0-4%. We present the clinical picture of a patient with hepatotoxicity due to mesalamine. A 79-year-old woman in the context of chronic diarrhea, a left-sided ulcerative colitis diagnosis was made, and treatment was initiated with oral mesalamine 4 g per day, and mesalamine suppositories. Before starting treatment, she had normal liver test results. After three months, she presented with headache, fatigue, and intermittent low fever. Her laboratory tests showed a liver profile with a cholestatic pattern, and elevation of inflammatory parameters. Mesalamine was suspended, and an extensive study was performed. Cholangioresonance reported intra and extrahepatic bile duct dilation without obstruction, and thickening of the intrahepatic bile duct. She progressed with worsening of the liver profile without signs of liver failure. A liver biopsy was performed, which showed chronic non-suppurative cholangitis with granulomas and focal concentric fibrosis related to medium-caliber bile ducts, and IgG4 stain was negative.