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IgG4-Related AIP — RACP Adult Medicine MCQ

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HardGastroenterologyIgG4-Related AIPRACP Adult Medicine

A 60-year-old man presents with obstructive jaundice and a pancreatic mass on CT. He has elevated IgG4 (6.2 g/L) and a diffusely enlarged 'sausage-shaped' pancreas on CT with loss of normal lobulation. Biliary biopsy shows storiform fibrosis and dense IgG4+ plasma cell infiltrate. What is the most likely cause?

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Correct answer: E — Autoimmune pancreatitis

IgG4-related autoimmune pancreatitis (type 1 AIP) presents with a sausage-shaped pancreas, elevated IgG4, obstructive jaundice, and characteristic histology (storiform fibrosis, IgG4+ plasma cells, obliterative phlebitis). It mimics pancreatic cancer clinically. Dramatic response to corticosteroids is both diagnostic and therapeutic. It may be part of systemic IgG4-related disease.

Reference: GESA – 2024 – Autoimmune Pancreatitis; International Consensus Diagnostic Criteria 2011