Pigmentary disorders: ochronosis: 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 · Pigmentary disorders: ochronosis

Sample item

A man has blue-black pigmentation of the ear cartilage and sclerae, dark urine on standing and early degenerative spinal arthritis. Which metabolite accumulates?

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

The answer and the reasoning

A. Homogentisic acid

Alkaptonuria results from homogentisate 1,2-dioxygenase deficiency, and oxidised homogentisic acid polymerises to deposit in connective tissue (ochronosis). Urine darkens on standing, and arthropathy develops in adulthood.

Option by option

  • A. Homogentisic acid (correct)

    Correct. Homogentisic acid accumulates.

  • B. Porphobilinogen

    Porphobilinogen accumulates in acute porphyrias.

  • C. Phenylalanine

    Phenylalanine accumulates in phenylketonuria.

  • D. Copper

    Copper accumulates in Wilson disease.

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 A, Homogentisic acid. Alkaptonuria results from homogentisate 1,2-dioxygenase deficiency, and oxidised homogentisic acid polymerises to deposit in connective tissue (ochronosis).

Why is "Porphobilinogen" not the answer?

Porphobilinogen accumulates in acute porphyrias.

Why is "Phenylalanine" not the answer?

Phenylalanine accumulates in phenylketonuria.

Why is "Copper" not the answer?

Copper accumulates in Wilson disease.

What concept does this question test?

It tests Pigmentary disorders: ochronosis in Dermatology. Urine darkens on standing, and arthropathy develops in adulthood.

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 Pigmentary disorders: ochronosis?

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.