Bilirubin metabolism: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Bilirubin metabolism

Sample item

A young man has mild intermittent unconjugated hyperbilirubinaemia after fasting and during illness, with normal liver enzymes and no haemolysis. What is the underlying defect?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Reduced activity of UDP-glucuronosyltransferase 1A1

Gilbert syndrome is a common benign condition due to reduced (about 30 percent) UGT1A1 activity, usually from a promoter TA-repeat expansion. Bilirubin rises with fasting and stress. Crigler-Najjar type I has absent activity and presents in the neonate with kernicterus.

Option by option

  • A. Absent UGT1A1 activity from birth

    Absent activity is Crigler-Najjar type I, severe from birth.

  • B. Defective canalicular excretion through MRP2

    MRP2 defect is Dubin-Johnson syndrome, with conjugated hyperbilirubinaemia.

  • C. Reduced activity of UDP-glucuronosyltransferase 1A1 (correct)

    Correct. Partial enzyme deficiency causes mild fluctuating unconjugated hyperbilirubinaemia.

  • D. Defective hepatic uptake due to biliary obstruction

    Obstruction causes conjugated hyperbilirubinaemia with raised ALP.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, Reduced activity of UDP-glucuronosyltransferase 1A1. Gilbert syndrome is a common benign condition due to reduced (about 30 percent) UGT1A1 activity, usually from a promoter TA-repeat expansion.

Why is "Absent UGT1A1 activity from birth" not the answer?

Absent activity is Crigler-Najjar type I, severe from birth.

Why is "Defective canalicular excretion through MRP2" not the answer?

MRP2 defect is Dubin-Johnson syndrome, with conjugated hyperbilirubinaemia.

Why is "Defective hepatic uptake due to biliary obstruction" not the answer?

Obstruction causes conjugated hyperbilirubinaemia with raised ALP.

What concept does this question test?

It tests Bilirubin metabolism in Biochemistry. Bilirubin rises with fasting and stress. Crigler-Najjar type I has absent activity and presents in the neonate with kernicterus.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Bilirubin metabolism?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.