Clinical and histologic features of Azathioprine-induced hepatotoxicity

Background: Hepatoxicity is a relative uncommon complication related with Azathioprine, however most studies were performed in inflammatory bowel diseases patients. The aim of this study is to report the clinical profile of patients with Azathioprine-induced hepatotoxicity.Methods: All medical records of patients received Azathioprine from 2010 to 2015 were retrospectively reviewed. Hepatotoxicity was defined as serum alanine aminotransferase (ALT) or aspatate aminotransferase (AST) or total bilirubin >2 times upper limit normal. Other causes of liver diseases were excluded. All subjects were followed until the resolution of liver injury.Results: Two-hundred and ninety-three patients receiving Azathioprine were retrospectively reviewed. Eight patients (2.7%) were diagnosed with Azathioprine-induced hepatotoxicity. The median age was 45 year with female preponderance. The latency to onset of liver injury ranged from 7 to 236 d, and 4 patients were symptomatic. Median peak levels were ALT 295U/L, alkaline phosphatase 169U/L, and total bilirubin 1mg/dl. According to R-ratio, mixed pattern (50%) was more frequent than cholestatic (37.5%) and hepatocellular pattern (12.5%). Liver biopsies were performed in 2 patients, and showed hepatocellular and canalicular cholestasis with mild portal and peri-portal inflammation. All patients recovered fully with a median time of 41.3 days. Two patients developed prolonged cholestasis >2 months, hence none had liver failure or required liver transplantation.Conclusion: Hepatotoxicity is relative uncommon in patients receiving Azathioprine, and predominantly is mixed hepatocellular and cholestatic in nature. Even though all patients recover fully after drug withdrawal, severe cholestasis can occur.