Sexually transmitted infections: 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 · Sexually transmitted infections

Sample item

A man has a painless, indurated, clean-based genital ulcer with firm, non-tender bilateral inguinal lymph nodes three weeks after unprotected sex. A VDRL test is non-reactive. Which test is most useful next?

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

The answer and the reasoning

A. Dark-field microscopy of the ulcer exudate

A painless indurated ulcer suggests a primary syphilitic chancre. Non-treponemal tests such as VDRL can be negative in early primary syphilis, so direct demonstration of Treponema pallidum by dark-field microscopy is the best test, with repeat serology later.

Option by option

  • A. Dark-field microscopy of the ulcer exudate (correct)

    Correct. Motile spirochaetes are seen directly in fluid from the chancre.

  • B. Tzanck smear for multinucleated giant cells

    A Tzanck smear identifies herpes simplex, which causes painful grouped vesicles and erosions.

  • C. Gram stain showing Gram-negative coccobacilli in chains

    Gram-negative coccobacilli in chains point to Haemophilus ducreyi, which causes a painful ragged ulcer.

  • D. Giemsa-stained smear for Donovan bodies

    Donovan bodies identify granuloma inguinale, which gives a beefy-red painless ulcer without marked nodes.

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, Dark-field microscopy of the ulcer exudate. A painless indurated ulcer suggests a primary syphilitic chancre.

Why is "Tzanck smear for multinucleated giant cells" not the answer?

A Tzanck smear identifies herpes simplex, which causes painful grouped vesicles and erosions.

Why is "Gram stain showing Gram-negative coccobacilli in chains" not the answer?

Gram-negative coccobacilli in chains point to Haemophilus ducreyi, which causes a painful ragged ulcer.

Why is "Giemsa-stained smear for Donovan bodies" not the answer?

Donovan bodies identify granuloma inguinale, which gives a beefy-red painless ulcer without marked nodes.

What concept does this question test?

It tests Sexually transmitted infections in Dermatology. Non-treponemal tests such as VDRL can be negative in early primary syphilis, so direct demonstration of Treponema pallidum by dark-field microscopy is the best test, with repeat serology later.

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 Sexually transmitted infections?

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.