Genetics: Patau syndrome: 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 · Genetics: Patau syndrome

Sample item

A newborn has cleft lip and palate, microphthalmia, scalp defects, postaxial polydactyly and holoprosencephaly. What is the likely karyotype?

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

The answer and the reasoning

D. 47,XX,+13

Patau syndrome is trisomy 13, characterised by midline defects, polydactyly, cutis aplasia and severe intellectual disability. Survival beyond infancy is uncommon. Cardiac defects and renal anomalies are frequent.

Option by option

  • A. 47,XX,+18

    Trisomy 18 shows overlapping fingers and rocker-bottom feet.

  • B. 45,X

    45,X is Turner syndrome.

  • C. 47,XX,+21

    Trisomy 21 shows upslanting eyes and a single palmar crease.

  • D. 47,XX,+13 (correct)

    Correct. These features indicate trisomy 13.

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 D, 47,XX,+13. Patau syndrome is trisomy 13, characterised by midline defects, polydactyly, cutis aplasia and severe intellectual disability.

Why is "47,XX,+18" not the answer?

Trisomy 18 shows overlapping fingers and rocker-bottom feet.

Why is "45,X" not the answer?

45,X is Turner syndrome.

Why is "47,XX,+21" not the answer?

Trisomy 21 shows upslanting eyes and a single palmar crease.

What concept does this question test?

It tests Genetics: Patau syndrome in Pediatrics. Survival beyond infancy is uncommon. Cardiac defects and renal anomalies are frequent.

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 Genetics: Patau syndrome?

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.