Mesalazine-Induced Interstitial Nephritis

5-aminosalicylate compounds (mesalazine, sulfasalazine) are widely used in therapy of inflammatory bowel diseases. Mesalazine-induced interstitial nephritis is a rare complication; however, the morbidity in an affected individual is high. Regular renal screening in patients treated with 5-aminosalicylate compounds is important. A 15-year-old boy with treated idiopathic proctocolitis, consequent mesalazine-induced nephritis, and a favorable response to corticotherapy is presented.