[Interstitial nephritis induced by mesalazine]

This report concerns the first case in Japan of interstitial nephritis induced by mesalazine, a new therapeutic agent for inflammatory bowel disease, such as ulcerative colitis. Twenty-two cases have already been reported in other countries. The patient, a 27-year-old woman, was treated with mesalazine for her ulcerative colitis at another hospital. At the beginning of her treatment, her serum creatinine level was within the normal range. After 12 months, this level increased up to 5.7 mg/dl. She was then referred to our hospital for renal investigation and therapy. A renal biopsy revealed that severe tubulo-interstitial nephritis had occurred. Her mesalazine treatment was withdrawn and prednisolone was administered. Her serum creatinine level decreased gradually. However, this level remained at about 2.8 mg/dl and stabilized at that level. She was then discharged from the hospital. Glomeruli appeared to have minor glomerular abnormalities except for one globally sclerosed glomerulus as observed by light microscopy. However, IgM and C3 deposition on glomeruli were also observed. Glomerular lesions were suspected from these histological findings. A similar case that showed IgM. C3 depositions in glomeruli has previously been reported. The possibility of glomerular lesions being induced by mesalazine should be further researched. From the summary of reported cases, a delay of diagnosis of interstitial nephritis induced by mesalazine has resulted in permanent irreversible renal failure. Intensive monitoring of renal function is required when a patient is treated with mesalazine.