Bilirubin metabolism: Dubin-Johnson syndrome: 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.

Try it

Biochemistry · Bilirubin metabolism: Dubin-Johnson syndrome

Sample item

A 20-year-old man has mild recurrent jaundice with conjugated hyperbilirubinaemia, normal ALT and ALP and a good prognosis. A liver biopsy done for another reason shows a grossly black liver with coarse pigment in hepatocytes. Which urinary finding fits this condition?

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

The answer and the reasoning

A. Normal total coproporphyrin with isomer I predominating

Dubin-Johnson syndrome is caused by mutations in MRP2 (ABCC2), the canalicular transporter for conjugated bilirubin, leaving a black melanin-like pigment in hepatocytes. Total urinary coproporphyrin is normal but over 80 percent is isomer I. In Rotor syndrome total coproporphyrin is markedly increased and the liver is not pigmented.

Option by option

  • A. Normal total coproporphyrin with isomer I predominating (correct)

    Correct. A normal total with isomer I predominance accompanies the MRP2 defect.

  • B. Raised delta-aminolevulinic acid and porphobilinogen

    Raised ALA and PBG indicate acute intermittent porphyria.

  • C. Markedly raised total coproporphyrin with a normal-coloured liver

    Markedly raised total coproporphyrin with a non-pigmented liver is the pattern of Rotor syndrome.

  • D. Raised uroporphyrin I with red urine that fluoresces under ultraviolet light

    Uroporphyrin I excess with fluorescent red urine suggests congenital erythropoietic porphyria, not a conjugated hyperbilirubinaemia.

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 A, Normal total coproporphyrin with isomer I predominating. Dubin-Johnson syndrome is caused by mutations in MRP2 (ABCC2), the canalicular transporter for conjugated bilirubin, leaving a black melanin-like pigment in hepatocytes.

Why is "Raised delta-aminolevulinic acid and porphobilinogen" not the answer?

Raised ALA and PBG indicate acute intermittent porphyria.

Why is "Markedly raised total coproporphyrin with a normal-coloured liver" not the answer?

Markedly raised total coproporphyrin with a non-pigmented liver is the pattern of Rotor syndrome.

Why is "Raised uroporphyrin I with red urine that fluoresces under ultraviole…" not the answer?

Uroporphyrin I excess with fluorescent red urine suggests congenital erythropoietic porphyria, not a conjugated hyperbilirubinaemia.

What concept does this question test?

It tests Bilirubin metabolism: Dubin-Johnson syndrome in Biochemistry. Total urinary coproporphyrin is normal but over 80 percent is isomer I. In Rotor syndrome total coproporphyrin is markedly increased and the liver is not pigmented.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: Dubin-Johnson syndrome?

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.