Case Prelude: A 34-year-old man presents to the clinic with a 6-month history of fatigue, generalized itching, and intermittent right upper quadrant abdominal discomfort. He also reports yellowing of his eyes for the past 2 weeks. His medical history is significant for ulcerative colitis diagnosed 10 years ago, for which he takes mesalamine. He denies fever, chills, weight loss, or changes in bowel habits. Physical Examination: Vitals: Blood pressure 120/80 mmHg, heart rate 80 bpm, temperature 36.8°C. General Appearance: Scleral icterus noted. Abdomen: Mild tenderness in the right upper quadrant without rebound or guarding. No hepatosplenomegaly or ascites. Skin: Evidence of excoriations due to scratching. Investigations: 1.Laboratory Tests: Elevated alkaline phosphatase (ALP): 550 U/L (normal: 44–147 U/L). Elevated gamma-glutamyltransferase (GGT): 120 U/L. Mildly elevated ALT: 90 U/L (normal: 10–40 U/L). Total bilirubin: 3.5 mg/dL (normal: 0.1–1.2 mg/dL). Positive p-ANCA antibody. 2.Imaging: Magnetic Resonance Cholangiopancreatography (MRCP): Irregular intrahepatic and extrahepatic bile ducts with alternating strictures and dilations (“beaded appearance”). 3.Colonoscopy: Active inflammation consistent with ulcerative colitis. What is the most likely diagnosis?
