IgG4-Related Disease — RACP Adult Medicine MCQ

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HardGastroenterology & HepatologyIgG4-Related DiseaseRACP Adult Medicine

A 55-year-old man presents with painless jaundice, dark urine, and pale stools. CT shows a dilated biliary system with no visible mass. MRCP shows a common bile duct stricture with upstream dilatation. His IgG4 level is markedly elevated at 8.5 g/L (normal <1.35 g/L). What is the most likely diagnosis?

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Correct answer: E — IgG4-related sclerosing cholangitis

Markedly elevated IgG4 (>2× upper limit) with a biliary stricture is highly suggestive of IgG4-related sclerosing cholangitis, part of IgG4-related disease. It is important to distinguish from cholangiocarcinoma (which it mimics). IgG4-RD responds dramatically to corticosteroids. However, histological confirmation is recommended where possible, and cholangiocarcinoma must be excluded before committing to immunosuppression. Other manifestations include autoimmune pancreatitis, retroperitoneal fibrosis, and orbital disease.

Reference: eTG – 2025 – Gastrointestinal; ACG – 2024 – IgG4-Related Disease Guidelines