STI: histology of syphilis: 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.

Try it

Dermatology · STI: histology of syphilis

Sample item

A biopsy from a firm, painless genital ulcer shows a dense perivascular infiltrate of plasma cells and lymphocytes with swelling of the endothelium and narrowing of small vessels. Which investigation on this tissue best demonstrates the organism?

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

The answer and the reasoning

B. Silver impregnation stain such as Warthin-Starry

Syphilis shows a plasma-cell-rich perivascular infiltrate with endarteritis. T. pallidum is too thin to be seen on routine stains, so silver impregnation methods or immunostaining are used in tissue.

Option by option

  • A. Ziehl-Neelsen stain

    Ziehl-Neelsen stains acid-fast bacilli such as mycobacteria, not treponemes.

  • B. Silver impregnation stain such as Warthin-Starry (correct)

    Correct. Silver stains such as Warthin-Starry demonstrate spirochaetes in tissue.

  • C. Gram stain

    Spirochaetes are too thin to be resolved by Gram stain.

  • D. Periodic acid-Schiff stain

    PAS stains fungi and glycogen, not spirochaetes.

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, Silver impregnation stain such as Warthin-Starry. Syphilis shows a plasma-cell-rich perivascular infiltrate with endarteritis.

Why is "Ziehl-Neelsen stain" not the answer?

Ziehl-Neelsen stains acid-fast bacilli such as mycobacteria, not treponemes.

Why is "Gram stain" not the answer?

Spirochaetes are too thin to be resolved by Gram stain.

Why is "Periodic acid-Schiff stain" not the answer?

PAS stains fungi and glycogen, not spirochaetes.

What concept does this question test?

It tests STI: histology of syphilis in Dermatology. T. pallidum is too thin to be seen on routine stains, so silver impregnation methods or immunostaining are used in tissue.

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 STI: histology of syphilis?

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.