Azathioprine is an immunosuppressive medication used in the management of many autoimmune conditions. Commonly reported adverse effects from azathioprine therapy are nausea and bone marrow suppression, while less common side effects include hepatotoxicity. We present the case of a 47-year-old man with a history of myasthenia gravis on azathioprine for 1 year, who presented to our institution with painless jaundice. On initial laboratory evaluation, the level of aspartate aminotransferase, alanine aminotransferase and total bilirubin were markedly elevated. Owing to the potential diagnosis of acute liver failure secondary to azathioprine toxicity, this medication was discontinued. A liver biopsy demonstrating drug-induced liver injury, along with high serum levels of 6-methylmercaptopurine nucleotide confirmed the diagnosis of azathioprine-induced hepatotoxicity. Upon discontinuation of the medication, the patient's transaminases and bilirubin levels improved steadily over the four-day hospital course. This case emphasises azathioprine's potential for hepatotoxicity, even 1 year after the initiation of its use.
2014 BMJ Publishing Group Ltd.