Papulosquamous disorders: Sjögren-Larsson syndrome: 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 · Papulosquamous disorders: Sjögren-Larsson syndrome

Sample item

A child has generalised ichthyosis from infancy, spastic diplegia and intellectual disability, and the retina shows glistening white dots. Which enzyme is deficient?

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

The answer and the reasoning

B. Fatty aldehyde dehydrogenase

Sjögren-Larsson syndrome is caused by deficiency of fatty aldehyde dehydrogenase (ALDH3A2). It combines ichthyosis, spastic paraplegia and intellectual disability with macular glistening dots.

Option by option

  • A. Phytanoyl-CoA hydroxylase

    Phytanoyl-CoA hydroxylase deficiency causes Refsum disease, with retinitis pigmentosa and neuropathy.

  • B. Fatty aldehyde dehydrogenase (correct)

    Correct. Fatty aldehyde dehydrogenase deficiency causes Sjögren-Larsson syndrome.

  • C. Steroid sulfatase

    Steroid sulfatase deficiency causes X-linked ichthyosis, with corneal opacities and no spasticity.

  • D. Transglutaminase 1

    Transglutaminase 1 deficiency causes lamellar ichthyosis with a collodion membrane.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is B, Fatty aldehyde dehydrogenase. Sjögren-Larsson syndrome is caused by deficiency of fatty aldehyde dehydrogenase (ALDH3A2).

Why is "Phytanoyl-CoA hydroxylase" not the answer?

Phytanoyl-CoA hydroxylase deficiency causes Refsum disease, with retinitis pigmentosa and neuropathy.

Why is "Steroid sulfatase" not the answer?

Steroid sulfatase deficiency causes X-linked ichthyosis, with corneal opacities and no spasticity.

Why is "Transglutaminase 1" not the answer?

Transglutaminase 1 deficiency causes lamellar ichthyosis with a collodion membrane.

What concept does this question test?

It tests Papulosquamous disorders: Sjögren-Larsson syndrome in Dermatology. It combines ichthyosis, spastic paraplegia and intellectual disability with macular glistening dots.

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 Papulosquamous disorders: Sjögren-Larsson syndrome?

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.