Genodermatoses: xeroderma pigmentosum: practice question

A Dermatology 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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Dermatology · Genodermatoses: xeroderma pigmentosum

Sample item

A child has severe sunburn on minimal exposure, freckling and early skin cancers. What is the underlying defect?

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

The answer and the reasoning

B. Defective nucleotide excision repair of UV-induced DNA damage

Xeroderma pigmentosum is an autosomal recessive disorder of nucleotide excision repair that cannot remove UV-induced pyrimidine dimers. Strict photoprotection is essential.

Option by option

  • A. Deficiency of tyrosinase

    Tyrosinase deficiency causes oculocutaneous albinism.

  • B. Defective nucleotide excision repair of UV-induced DNA damage (correct)

    Correct. Failure to repair pyrimidine dimers causes UV hypersensitivity and tumours.

  • C. Defective homologous recombination

    Homologous recombination defects underlie BRCA-related cancers.

  • D. Defective mismatch repair

    Mismatch repair defects cause Lynch syndrome.

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 Dermatology questions

Questions about this Dermatology question

What is the answer to this Dermatology question?

The best answer is B, Defective nucleotide excision repair of UV-induced DNA damage. Xeroderma pigmentosum is an autosomal recessive disorder of nucleotide excision repair that cannot remove UV-induced pyrimidine dimers.

Why is "Deficiency of tyrosinase" not the answer?

Tyrosinase deficiency causes oculocutaneous albinism.

Why is "Defective homologous recombination" not the answer?

Homologous recombination defects underlie BRCA-related cancers.

Why is "Defective mismatch repair" not the answer?

Mismatch repair defects cause Lynch syndrome.

What concept does this question test?

It tests Genodermatoses: xeroderma pigmentosum in Dermatology. Strict photoprotection is essential.

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 Genodermatoses: xeroderma pigmentosum?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.