INTRODUCTION: Vismodegib, a hedgehog pathway inhibitor used to treat locally advanced and metastatic basal cell carcinoma, can lead to severe hepatotoxicity. Patients who develop nausea, loss of appetite, and dysgeusia should have liver enzymes evaluated. Early detection of liver insult could lead to early discontinuation of the drug to prevent worsening liver injury, further workup and unnecessary hospitalization. CASE DESCRIPTION/METHODS: A 53 year old female with invasive basal cell carcinoma on vismodegib, presented with loss of appetite, RUQ abdominal pain and jaundice. Labs revealed a total bilirubin of 7.4 mg/dL, alkaline phosphatase 545 IU/L, AST 163 IU/L, and ALT 471 IU/L. Viral hepatitis and autoimmune panel was unremarkable. MRCP and an endoscopic ultrasound did not show any biliary obstruction. However, the biliary ducts appeared unusually small. Her bilirubin continued to increase, and the idea of vismodegib causing cholestatic liver injury and vanishing bile duct syndrome was entertained. However, ERCP revealed a normal cholangiogram. Liver biopsy was pursued and showed marked zone 3 canalicula cholestasis and marked duct injury in portal tracts suggesting vismodegib causing cholestatic liver injury. DISCUSSION: There have been a few cases now reporting vismodegib-induced liver injury. Luckily our patient slowly improved with drug withdrawal. However, there has been life-threatening hepatotoxicity and even death, especially in patients taking drugs with potential hepatotoxic effects. Liver enzymes can mimic the pattern of acute viral or autoimmune hepatitis or ischemic liver injury. Our initial suspicion given our patient's MRCP and EUS findings, with bile ducts appearing abnormally small, was drug-induced vanishing bile duct syndrome. Vanishing bile duct syndrome in adults is typically caused by autoimmune diseases, neoplasms such as Hodgkin’s lymphoma, infections such as CMV and drugs such as allopurinol. The diagnosis is made through liver biopsy containing at least 10 portal tracts, showing loss of interlobular bile ducts in > 50% of the portal tracts. Clinically, patients will have fatigue, weight loss, loss of appetite, and abdominal pain as a result of intrahepatic cholestasis. Treatment includes discontinuation of offending drug but others have trialed ursodiol. Our patient’s liver biopsy did not suggest this rare syndrome but we suspect that if she had continued vismodegib, her outcome could have been worse and her liver biopsy could have progressed to vanishing bile duct syndrome.Figure 1.: Magnetic resonance cholangiopancreatography did not show any evidence of obstruction. Biliary ducts appeared small.Figure 2.: Endoscopic retrograde cholangiopancreatography was unremarkable, without evidence of obstruction.