Peripheral T-cell lymphoma mimicking 5-aminosalicylate hypersensitivity in ulcerative colitis.

5-aminosalicylates (5-ASA) remain an important strategy in the induction and maintenance of remission of inflammatory bowel diseases especially in ulcerative colitis. The prototypical drug of this class, sulfasalazine is generally well tolerated with severe hypersensitivity reactions and hepatotoxicity also described within the literature. When approaching a patient with an adverse reaction to 5-ASA, it can be difficult to differentiate clinically between a sulfa allergy versus a 5-ASA allergy versus a malignancy. We report on a case with initial signs and symptoms suggestive of a sulfa/5-ASA allergy that was subsequently found to be malignant in nature.