Pigmentary disorders: phytophotodermatitis: 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: phytophotodermatitis

Sample item

A bartender squeezes limes outdoors in bright sun. A day later he has linear streaky erythema and blisters on the hands that heal with brown streaky pigmentation. Which constituent of the juice is responsible?

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

The answer and the reasoning

C. Furocoumarins that sensitise the skin to UVA

Phytophotodermatitis is a phototoxic reaction to furocoumarins (psoralens) in limes, celery, parsnip and figs, activated by UVA. It appears within 24 to 72 hours in bizarre streaks or drip patterns and often leaves post-inflammatory hyperpigmentation. It does not need prior sensitisation.

Option by option

  • A. Salicylates producing a photoallergic reaction

    Salicylates in the juice do not cause photoallergy, and a reaction within a day in a first exposure points to phototoxicity.

  • B. Limonene acting as a delayed-type allergen

    Limonene can cause allergic contact dermatitis, which requires prior sensitisation and is not sunlight dependent.

  • C. Furocoumarins that sensitise the skin to UVA (correct)

    Correct. Furocoumarins plus UVA cause a phototoxic reaction with streaky blisters and later hyperpigmentation.

  • D. Citric acid acting as a direct irritant

    Citric acid can irritate, but it would not need sunlight and would not leave a streaky pattern tied to sun exposure.

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 C, Furocoumarins that sensitise the skin to UVA. Phytophotodermatitis is a phototoxic reaction to furocoumarins (psoralens) in limes, celery, parsnip and figs, activated by UVA.

Why is "Salicylates producing a photoallergic reaction" not the answer?

Salicylates in the juice do not cause photoallergy, and a reaction within a day in a first exposure points to phototoxicity.

Why is "Limonene acting as a delayed-type allergen" not the answer?

Limonene can cause allergic contact dermatitis, which requires prior sensitisation and is not sunlight dependent.

Why is "Citric acid acting as a direct irritant" not the answer?

Citric acid can irritate, but it would not need sunlight and would not leave a streaky pattern tied to sun exposure.

What concept does this question test?

It tests Pigmentary disorders: phytophotodermatitis in Dermatology. It appears within 24 to 72 hours in bizarre streaks or drip patterns and often leaves post-inflammatory hyperpigmentation. It does not need prior sensitisation.

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 Pigmentary disorders: phytophotodermatitis?

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.