Chronic Tubulointerstitial Nephritis Induced by 5-aminosalicylate in an Ulcerative Colitis Patient: a Rare but Serious Adverse Event

The 5-aminosalicylate is widely prescribed in inflammatory bowel disease patients. Its potential for renal damage has been seldom described. We report a case of a 23-year-old man who started 5-aminosalicylate after being diagnosed with ulcerative colitis. One year after, a significant decline on his creatinine clearance was noted, however, at that time, he was on an acute flare of his bowel disease and the 5-aminosalicylate dose was increased. Six months later, his renal function kept worsening and, on drug-induced toxicity suspicion, 5-aminosalicylate was halted and a kidney biopsy demonstrated a chronic tubulointerstitial nephritis. Steroids and azathioprine were started leading to partial recovery and stabilisation of his renal function. Physicians who prescribe 5-aminosalicylate to patients with inflammatory bowel disease should be aware of this adverse event.