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Asthma — UKMLA MCQ

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HardRespiratory MedicineAsthmaUKMLAMRCP Part 1

A 23-year-old has recurrent months-long episodes of intense pruritus and conjugated jaundice separated by years of completely normal liver tests. During attacks, bile acids are markedly raised but gamma-glutamyl transferase remains low. Imaging shows no obstruction. Which genetic defect most plausibly causes type 1 disease?

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Correct answer: D — ATP8B1 deficiency

The best answer is “ATP8B1 deficiency”. Mild-to-moderate ATP8B1 deficiency causes benign recurrent intrahepatic cholestasis type 1. Episodes of low-GGT cholestasis and severe pruritus alternate with symptom-free intervals, although the term benign can understate morbidity and some patients progress. ABCB11 causes BRIC type 2, while ABCB4 disease usually has high GGT because of bile-duct injury. UGT1A1 causes unconjugated hyperbilirubinaemia, JAG1 causes Alagille syndrome, and HFE variants cause iron loading rather than episodic cholestasis.

Reference: ATP8B1 Deficiency — GeneReviews: https://www.ncbi.nlm.nih.gov/books/NBK1297/