What Causes Elevation In Bilirubin Levels While On Azathioprine?

I am diagnosed with autoimmune hepatitis and was prescribed with prednisone and azathioprine. I took them for one month and I have jaundiced. I was admitted to the hospital because my liver function enzymes are high especially the bilirubin. The doctor stopped the azathioprine for 3 days and still my bilirubin is high now it is 293. My ultrasound shows no obstruction, no bleeding and no varices. I need help or explanation to this Thank you,