MSFinals-1329

MSFinals-1329

A 28-year-old man presents with generalised pruritus, right upper quadrant pain and jaundice for the past month. He has a history of recurrent bloody bowel movements and painful defecation and is now being treated with sulfasalazine. His previous colonoscopy has shown superficial mucosal ulceration and inflammation, with many pseudopolyps involving the distal rectum up to the middle third of the transverse colon. On abdominal examination, the liver is slightly enlarged and tender. Total bilirubin level is 102.6 μmol/l and indirect bilirubin level 47.9 μmol/l. Alkaline phosphatase and γ-glutamyltransferase concentrations are moderately increased. Alanine aminotransferase and aspartate aminotransferase levels are mildly elevated.
Which of the following autoantibodies is most likely to be positive in this patient?