In primary sclerosing cholangitis (PSC), the characteristic histological pattern is 'onion-skin fibrosis' around bile ducts. PSC is strongly associated with which inflammatory bowel disease, and what percentage of PSC patients have this association?

• A Ulcerative colitis; approximately 70–80% of PSC patients have IBD, usually pancolitis ✓
• B Crohn's disease; approximately 50% of PSC patients have ileocolonic Crohn's
• C Microscopic colitis; approximately 30% of PSC patients have microscopic colitis
• D Ulcerative colitis; approximately 30–40% of PSC patients have proctitis only

Explanation

PSC is strongly associated with inflammatory bowel disease in approximately 70–80% of patients, with the vast majority having ulcerative colitis (pancolitis pattern). However, paradoxically, treating UC does not improve PSC, and PSC can worsen even after colectomy, suggesting independent pathogenic mechanisms. PSC patients with IBD have a substantially higher risk of colorectal dysplasia and cholangiocarcinoma compared to either disease alone. The 'onion-skin' periductal fibrosis with bile duct obliteration eventually leads to biliary cirrhosis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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