paeds505

A 16-year-old boy, known case of Crohn’s disease presents to the clinic with jaundice. His labs reveal an elevated alkaline phosphatase level. AST, ALT, albumin and clotting are in normal range. Antineutrophil cytoplasmic antibody level is positive. Radiological examination shows multi-focal strictures and irregularity of both intra and extra hepatic bile ducts which has resulted in a ‘beads on a string’ appearance. Which of the following is the most likely diagnosis?