Mesalamine-induced refractory fever and progressive increase in creatinine level and leukocyte count in a patient with enteropathic arthritis.

A 22-year-old female patient was admitted to our hospital with bloody diarrhea lasting for 6 weeks, erythema nodosum, and bilateral arthritis in the knees. Until the diagnosis, metronidazole 1500 mg/day (IV) was ordered, but the symptoms did not resolve, and on the seventh day, a colonoscopic evaluation was planned. The colonoscopic and pathological examination was compatible with ulcerative colitis, and the sacroiliac MRI scan revealed bilateral sacroiliitis. She was diagnosed as ulcerative colitis and enteropathic arthritis. Firstly, 60 mg/day methylprednisolone was ordered, and 4 days later, 2000 mg/day of mesalamine was added to the treatment protocol. After the addition of mesalamine, a fever of 39.5°C developed. First, she was evaluated for additional infections, but an infectious reason could not be found. Parallel to the fever, renal function impairment also occurred. Although the basal creatinine level was 0.87 mg/dL, it increased up to 2.46 mg/dL in 4 days. After the cessation of mesalamine treatment, the fever disappeared, and the creatinine level came to normal levels. Now, she is on a treatment protocol with azathioprine 150 mg/day, and the steroid has been tapered slowly and stopped.