Child and adolescent psychiatry: Prader-Willi syndrome: practice question

A Psychiatry 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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Psychiatry · Child and adolescent psychiatry: Prader-Willi syndrome

Sample item

A child had marked hypotonia and poor feeding as an infant. At 5 years he has insatiable hunger, obesity, mild intellectual disability, hypogonadism, temper outbursts and skin picking. What is the underlying genetic abnormality?

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

The answer and the reasoning

B. Loss of paternal chromosome 15q11-q13 genes

Prader-Willi syndrome results from lack of expression of the paternally inherited 15q11-q13 region, by deletion or maternal uniparental disomy, because of genomic imprinting. Loss of the maternal copy of the same region causes Angelman syndrome.

Option by option

  • A. Loss of maternal chromosome 15q11-q13 genes

    Loss of the maternal copy causes Angelman syndrome with seizures and inappropriate laughter.

  • B. Loss of paternal chromosome 15q11-q13 genes (correct)

    Correct. Absent paternal 15q11-q13 expression causes Prader-Willi syndrome.

  • C. CGG repeat expansion in the FMR1 gene

    CGG expansion in FMR1 causes fragile X syndrome.

  • D. Trisomy 21

    Trisomy 21 causes Down syndrome, which has a different phenotype.

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 Psychiatry question

What is the answer to this Psychiatry question?

The best answer is B, Loss of paternal chromosome 15q11-q13 genes. Prader-Willi syndrome results from lack of expression of the paternally inherited 15q11-q13 region, by deletion or maternal uniparental disomy, because of genomic imprinting.

Why is "Loss of maternal chromosome 15q11-q13 genes" not the answer?

Loss of the maternal copy causes Angelman syndrome with seizures and inappropriate laughter.

Why is "CGG repeat expansion in the FMR1 gene" not the answer?

CGG expansion in FMR1 causes fragile X syndrome.

Why is "Trisomy 21" not the answer?

Trisomy 21 causes Down syndrome, which has a different phenotype.

What concept does this question test?

It tests Child and adolescent psychiatry: Prader-Willi syndrome in Psychiatry. Loss of the maternal copy of the same region causes Angelman syndrome.

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 Child and adolescent psychiatry: Prader-Willi syndrome?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry 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.