Genodermatoses: X-linked ichthyosis: 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.

Try it

Dermatology · Genodermatoses: X-linked ichthyosis

Sample item

A boy has dark, large, adherent scales on the neck and trunk beginning in infancy, with comma-shaped corneal opacities, and his maternal uncle is affected. Which enzyme is deficient?

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

The answer and the reasoning

C. Steroid sulfatase

X-linked recessive ichthyosis results from deletion of the STS gene at Xp22.3 encoding steroid sulfatase, so cholesterol sulphate accumulates and stratum corneum desquamation is impaired. Cryptorchidism and prolonged labour in carrier mothers are associated.

Option by option

  • A. Tyrosinase

    Tyrosinase deficiency causes oculocutaneous albinism.

  • B. Filaggrin

    Filaggrin deficiency causes ichthyosis vulgaris.

  • C. Steroid sulfatase (correct)

    Correct. Steroid sulfatase deficiency is the cause.

  • D. Transglutaminase 1

    Transglutaminase 1 deficiency causes lamellar ichthyosis.

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 C, Steroid sulfatase. X-linked recessive ichthyosis results from deletion of the STS gene at Xp22.

Why is "Tyrosinase" not the answer?

Tyrosinase deficiency causes oculocutaneous albinism.

Why is "Filaggrin" not the answer?

Filaggrin deficiency causes ichthyosis vulgaris.

Why is "Transglutaminase 1" not the answer?

Transglutaminase 1 deficiency causes lamellar ichthyosis.

What concept does this question test?

It tests Genodermatoses: X-linked ichthyosis in Dermatology. 3 encoding steroid sulfatase, so cholesterol sulphate accumulates and stratum corneum desquamation is impaired. Cryptorchidism and prolonged labour in carrier mothers are associated.

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: X-linked ichthyosis?

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.