Neonatology: mechanism of phototherapy: practice question

A Pediatrics 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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Pediatrics · Neonatology: mechanism of phototherapy

Sample item

Which mechanism mainly lowers serum bilirubin during phototherapy for neonatal jaundice?

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

The answer and the reasoning

A. Structural isomerisation to lumirubin, excreted without conjugation

Light converts bilirubin in the skin and superficial capillaries into configurational isomers and, irreversibly, structural isomer lumirubin. These water-soluble forms are excreted in bile and urine without the need for conjugation.

Option by option

  • A. Structural isomerisation to lumirubin, excreted without conjugation (correct)

    Correct. Lumirubin formation is the main route, and it needs no conjugation.

  • B. Reduction of enterohepatic circulation of bilirubin

    Reduced enterohepatic circulation would be the effect of early frequent feeding and not of light.

  • C. Induction of hepatic glucuronyl transferase

    Enzyme induction is the action of phenobarbital, not of light.

  • D. Destruction of fetal haemoglobin in the skin

    Phototherapy does not destroy haemoglobin; it alters bilirubin.

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.

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Questions about this Pediatrics question

What is the answer to this Pediatrics question?

The best answer is A, Structural isomerisation to lumirubin, excreted without conjugation. Light converts bilirubin in the skin and superficial capillaries into configurational isomers and, irreversibly, structural isomer lumirubin.

Why is "Reduction of enterohepatic circulation of bilirubin" not the answer?

Reduced enterohepatic circulation would be the effect of early frequent feeding and not of light.

Why is "Induction of hepatic glucuronyl transferase" not the answer?

Enzyme induction is the action of phenobarbital, not of light.

Why is "Destruction of fetal haemoglobin in the skin" not the answer?

Phototherapy does not destroy haemoglobin; it alters bilirubin.

What concept does this question test?

It tests Neonatology: mechanism of phototherapy in Pediatrics. These water-soluble forms are excreted in bile and urine without the need for conjugation.

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 Neonatology: mechanism of phototherapy?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.