A 19-year-old student notices mild yellow discolouration of eyes during examination week. Bilirubin is 2.8 mg/dL, entirely unconjugated; ALT, AST, and ALP are normal; urine dipstick shows no bilirubin. Haemoglobin and reticulocyte count are normal. Fasting reproduces the rise. What is the underlying defect?
- A Defective canalicular multidrug resistance-associated protein causing conjugated hyperbilirubinaemia
- B Reduced activity of UDP-glucuronosyltransferase 1A1 in the liver ✓
- C Autoimmune destruction of small intrahepatic bile ducts
- D Defect in bilirubin uptake due to OATP transporter mutation with black pigment stones
Correct answer: B. Reduced activity of UDP-glucuronosyltransferase 1A1 in the liver
Explanation
Gilbert syndrome results from reduced hepatic UDP-glucuronosyltransferase 1A1 activity, roughly 30 percent of normal, causing mild unconjugated hyperbilirubinaemia below 4 mg/dL with otherwise normal liver tests. Levels rise with fasting, illness, and exertion because reduced caloric intake lowers UGT activity. Dubin-Johnson involves MRP2 defect with conjugated hyperbilirubinaemia, and Crigler-Najjar type II produces far higher levels.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.