Retina: gyrate atrophy: practice question

A Ophthalmology 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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Ophthalmology · Retina: gyrate atrophy

Sample item

A 12-year-old with myopia and night blindness has sharply demarcated, scalloped patches of chorioretinal atrophy in the mid-periphery and early cataract. Plasma amino acid analysis shows a markedly raised urea cycle amino acid that falls with vitamin B6. Which enzyme is deficient?

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

The answer and the reasoning

D. Ornithine aminotransferase

Gyrate atrophy is an autosomal recessive deficiency of ornithine aminotransferase, causing hyperornithinaemia. Management includes an arginine-restricted diet and vitamin B6 in responsive patients.

Option by option

  • A. Galactokinase

    Galactokinase deficiency causes infantile cataract without chorioretinal atrophy.

  • B. Cystathionine beta-synthase

    Cystathionine beta-synthase deficiency causes homocystinuria with downward ectopia lentis.

  • C. Phytanoyl-CoA hydroxylase

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

  • D. Ornithine aminotransferase (correct)

    Correct. Ornithine aminotransferase deficiency causes hyperornithinaemia and gyrate chorioretinal atrophy.

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 Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is D, Ornithine aminotransferase. Gyrate atrophy is an autosomal recessive deficiency of ornithine aminotransferase, causing hyperornithinaemia.

Why is "Galactokinase" not the answer?

Galactokinase deficiency causes infantile cataract without chorioretinal atrophy.

Why is "Cystathionine beta-synthase" not the answer?

Cystathionine beta-synthase deficiency causes homocystinuria with downward ectopia lentis.

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

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

What concept does this question test?

It tests Retina: gyrate atrophy in Ophthalmology. Management includes an arginine-restricted diet and vitamin B6 in responsive patients.

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 Retina: gyrate atrophy?

Group the red eye by what to examine and what the pupil does. Then use the flashcards and the other Ophthalmology 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.