Infections: bacterial, viral, fungal, parasitic: Paederus dermatitis: 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 · Infections: bacterial, viral, fungal, parasitic: Paederus dermatitis

Sample item

During the monsoon a farmer wakes with linear streaks of erythema and vesicles on the neck, with a burning sensation and mirror-image lesions where two skin folds touched. He had brushed off a small slender beetle in the night. Which agent caused this eruption?

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

The answer and the reasoning

B. Pederin released from a crushed rove beetle

Paederus rove beetles do not bite. When crushed or brushed on the skin they release pederin, a vesicant that gives linear or kissing vesicular lesions after a delay of several hours. Treatment is washing the area, a topical steroid and cool compresses.

Option by option

  • A. Salivary antigens of the itch mite

    Mite antigens cause burrows and nocturnal itch, not linear blisters with burning.

  • B. Pederin released from a crushed rove beetle (correct)

    Correct. Pederin is a vesicant toxin, and kissing lesions on opposed skin folds are the classic clue.

  • C. Hairs of a stinging caterpillar

    Caterpillar hairs cause an immediate stinging urticarial or papular reaction, not linear vesicles after a night.

  • D. Allergen of poison ivy sap

    Rhus allergen causes a type IV contact dermatitis in sensitised people and is not linked to a beetle.

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 B, Pederin released from a crushed rove beetle. Paederus rove beetles do not bite.

Why is "Salivary antigens of the itch mite" not the answer?

Mite antigens cause burrows and nocturnal itch, not linear blisters with burning.

Why is "Hairs of a stinging caterpillar" not the answer?

Caterpillar hairs cause an immediate stinging urticarial or papular reaction, not linear vesicles after a night.

Why is "Allergen of poison ivy sap" not the answer?

Rhus allergen causes a type IV contact dermatitis in sensitised people and is not linked to a beetle.

What concept does this question test?

It tests Infections: bacterial, viral, fungal, parasitic: Paederus dermatitis in Dermatology. When crushed or brushed on the skin they release pederin, a vesicant that gives linear or kissing vesicular lesions after a delay of several hours. Treatment is washing the area, a topical steroid and cool compresses.

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 Infections: bacterial, viral, fungal, parasitic: Paederus dermatitis?

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.