Infections: bacterial, viral, fungal, parasitic: onset of itch in first scabies infestation: 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: onset of itch in first scabies infestation

Sample item

A student sharing a hostel room develops intense nocturnal itch only 4 weeks after first exposure to a scabies carrier, although mites were present from the start. What best explains the delay?

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

The answer and the reasoning

A. Delayed-type hypersensitivity to mite antigens

Itch in scabies is largely a type IV hypersensitivity response to mite proteins, faeces and eggs. It takes 3 to 6 weeks to develop in a first infestation but only 1 to 3 days on re-exposure.

Option by option

  • A. Delayed-type hypersensitivity to mite antigens (correct)

    Correct. A delayed-type hypersensitivity reaction takes weeks to develop in a first infestation.

  • B. Secondary bacterial infection of burrows

    Secondary infection causes pustules and crusting and does not explain the timing of itch.

  • C. Immediate IgE-mediated anaphylaxis to mite saliva

    Immediate IgE-mediated anaphylaxis would cause itch or urticaria within minutes.

  • D. Slow multiplication of the mite in the stratum granulosum

    Mites live in the stratum corneum, not the granulosum, and the delay is immunological and not due to slow multiplication.

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 A, Delayed-type hypersensitivity to mite antigens. Itch in scabies is largely a type IV hypersensitivity response to mite proteins, faeces and eggs.

Why is "Secondary bacterial infection of burrows" not the answer?

Secondary infection causes pustules and crusting and does not explain the timing of itch.

Why is "Immediate IgE-mediated anaphylaxis to mite saliva" not the answer?

Immediate IgE-mediated anaphylaxis would cause itch or urticaria within minutes.

Why is "Slow multiplication of the mite in the stratum granulosum" not the answer?

Mites live in the stratum corneum, not the granulosum, and the delay is immunological and not due to slow multiplication.

What concept does this question test?

It tests Infections: bacterial, viral, fungal, parasitic: onset of itch in first scabies infestation in Dermatology. It takes 3 to 6 weeks to develop in a first infestation but only 1 to 3 days on re-exposure.

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: onset of itch in first scabies infestation?

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.