Genetic and metabolic disorders: biotinidase deficiency: 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 · Genetic and metabolic disorders: biotinidase deficiency

Sample item

A 3-month-old has seizures, hypotonia, a scaly skin rash and hair loss. Blood shows metabolic acidosis with raised lactate, and urine has an abnormal organic acid profile. Which treatment corrects the condition?

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

The answer and the reasoning

B. Oral biotin

Biotinidase deficiency impairs recycling of biotin, so multiple carboxylases fail, giving organic aciduria, lactic acidosis, seizures, rash, alopecia and later hearing and optic loss. Lifelong oral biotin prevents and reverses most features and is why it is on newborn screening in some programmes. Zinc deficiency causes a similar rash but not seizures with organic aciduria.

Option by option

  • A. Oral zinc

    Zinc treats acrodermatitis enteropathica, which lacks organic aciduria and seizures.

  • B. Oral biotin (correct)

    Correct. Biotin replacement restores carboxylase activity.

  • C. Pyridoxine

    Pyridoxine treats pyridoxine-dependent seizures but does not correct organic aciduria and rash.

  • D. Thiamine

    Thiamine treats thiamine-responsive disorders such as beriberi or maple syrup urine disease variants.

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 B, Oral biotin. Biotinidase deficiency impairs recycling of biotin, so multiple carboxylases fail, giving organic aciduria, lactic acidosis, seizures, rash, alopecia and later hearing and optic loss.

Why is "Oral zinc" not the answer?

Zinc treats acrodermatitis enteropathica, which lacks organic aciduria and seizures.

Why is "Pyridoxine" not the answer?

Pyridoxine treats pyridoxine-dependent seizures but does not correct organic aciduria and rash.

Why is "Thiamine" not the answer?

Thiamine treats thiamine-responsive disorders such as beriberi or maple syrup urine disease variants.

What concept does this question test?

It tests Genetic and metabolic disorders: biotinidase deficiency in Pediatrics. Lifelong oral biotin prevents and reverses most features and is why it is on newborn screening in some programmes. Zinc deficiency causes a similar rash but not seizures with organic aciduria.

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 Genetic and metabolic disorders: biotinidase deficiency?

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.