Acute Pancreatitis Induced by Azathioprine and 6-mercaptopurine Proven by Single and Low Dose Challenge Testing in a Child with Crohn Disease

We report here a case of drug-induced acute pancreatitis proved by elimination and single, low dose challenge test in a child with Crohn disease. A 14-year-old boy with moderate/severe Crohn disease was admitted due to high fever and severe epigastric pain during administration of mesalazine and azathioprine. Blood test and abdominal ultrasonography revealed acute pancreatitis. After discontinuance of the medication and supportive care, the symptoms and laboratory findings improved. A single, low dose challenge test was done to confirm the relationship of the adverse drug reaction and acute pancreatitis, and to discriminate the responsible drug. Azathioprine and 6-mercaptopurine showed positive responses, and mesalazine showed a negative response. We introduce the method of single, low dose challenge test and its interpretation for drug-induced pancreatitis.