Inflammatory Bowel Disease USMLE Step 1 Practice Question

A 45-year-old woman with a 15-year history of ulcerative colitis presents to the clinic with progressive fatigue, dyspnea on exertion, and mild jaundice. She denies abdominal pain or diarrhea flares. Vital signs are normal. Laboratory studies show: Hemoglobin: 8.5 g/dL Mean corpuscular volume: 88 fL Reticulocyte count: 8.2% (elevated) Indirect bilirubin: 2.8 mg/dL Direct bilirubin: 0.3 mg/dL LDH: 580 U/L Haptoglobin: <10 mg/dL Direct antiglobulin test (Coombs): Positive Which of the following autoimmune conditions most likely accounts for this patient's clinical presentation?