Methaemoglobinaemia and renal failure following mesalazine for treatment of inflammatory bowel disease.

We report the first case of methaemoglobinaemia induced by mesalazine. A woman suffering diarrhea and abdominal pain was initially treated with sulfamethoxazole–trimethoprim (TMP–SMX) and metronidazole for suspected infectious colitis. The treatment was stopped after ten days and she was referred to a gastroenterologist. A colonoscopy showed features resembling inflammatory bowel disease. Histology was in favor of Crohn's disease. The antibiotic was withdrawn and the patient was sent back home with steroids and 6 g/day of mesalazine orally. One week later, she was readmitted for asthenia, cyanosis and confusion. Physical examination revealed polypnea while the blood pressure, pulse rate and oxygen saturationwere unremarkable. Laboratory tests are shown in Table 1. A diagnosis of drug-induced methaemoglobinaemia was made. The patient was transferred to the intensive care unit and treated with calcium gluconate and continuous veno-venous hemofiltration. Mesalazine was withdrawn. She was subsequently treated with hemofiltration and intravenous methylene blue. The outcome was favorable with normal diuresis within two days and a reduction of the serum creatinine level and methaemoglobin concentration (Table 1). Methaemoglobinaemia is characterized by the presence of a higher than normal level of methaemoglobin in the blood. Methaemoglobin is a form of hemoglobin that contains ferric iron and has a decreased ability to bind oxygen. This leads to an overall reduced ability of the red blood cells to release oxygen to tissues, inducing tissue hypoxia. Normal methaemoglobin level is below 1% of total hemoglobin. Spontaneously formed methaemoglobin is normally reduced by protective enzyme systems. Two types of methaemoglobinaemia are described: the congenital form and the acquired form, as the consequence of exposure to exogenous oxidizing drugs and metabolites [1]. Clinical presentation is related to tissue hypoxia and includes cyanosis, headache, fatigue, dizziness, cerebral ischemia, coma and eventually death. Treatment of acquired methaemoglobinaemia is based on drug withdrawal and intravenous methylene blue [2]. Hemofiltration is used in case of associated acute renal failure. We describe the first case of methaemoglobinaemia induced by mesalazine. The time concordance and the complete