Severe hepatotoxicity associated with use of a dietary supplement containing usnic acid.

Dietary supplements containing usnic acid are marketed for weight loss and have been associated with hepatotoxicity. The specific ingredient responsible for the hepatotoxicity is currently unknown. We describe 2 patients who developed severe hepatotoxicity within 3 months of taking a dietary supplement containing usnic acid. One patient developed fulminant hepatic failure requiring emergency liver transplantation; the other developed submassive hepatic necrosis but did not require transplantation. Thorough investigation, including histopathological examination of the liver, revealed no other cause of acute liver injury. Usnic acid hepatotoxicity should be considered as a possible etiologic factor in patients presenting with fulminant hepatic failure, especially if they have been taking dietary supplements for weight reduction.