Idiosyncratic drug allergic phenprocoumon-induced hepatitis with subacute liver failure initially misdiagnosed as autoimmune hepatitis

Background: Coumarin anticoagulants are known to cause hepatotoxicity, but only a few cases have been reported. Coumarins are usually administered fol lowing cardiovascular surgery and the differential diagnosis is post-transf usion hepatitis. Methods: We report the case of a 46-year-old woman who pre sented with jaundice, elevated liver function tests, positive antinuclear a nd smooth muscle antibodies following prodromal signs of fatigue and nausea . The patient had been treated with phenprocoumon for 5 months in order to prevent thromboembolism after two strokes assumed to be due to an open fora men ovate and an aneurysmatic atrial septum. Results: There was no evidence of viral or other causes of hepatitis. The patient rapidly developed subac ute liver failure with encephalopathy and phenprocoumon treatment was stopp ed. With intensive care support, as well as high-dose prednisolone treatmen t, she recovered. Owing to positive antinuclear and smooth muscle antibodie s, the initial diagnosis 'acute autoimmune hepatitis with liver failure' wa s made. Conclusion: The lack of hypergammaglobulinaemia and the rapid recur rence of hepatitis following re-exposure to phenprocoumon led to the final diagnosis of phenprocoumon-induced idiosyncratic drug allergic hepatitis wi th secondary autoimmune phenomena.