Bacterial 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 · Bacterial infections

Sample item

A middle-aged diabetic man has well-defined, dry, brown-red, finely scaly patches in the groin and axillae. Under a Wood's lamp they glow coral red. What is the causative organism?

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

The answer and the reasoning

C. Corynebacterium minutissimum

Erythrasma is a superficial infection of the stratum corneum in intertriginous areas, and diabetes and obesity predispose to it. The organism produces porphyrins that fluoresce coral red under Wood's light. Erythromycin is an effective treatment.

Option by option

  • A. Trichophyton rubrum

    Trichophyton rubrum causes tinea cruris, which has an active raised edge and does not typically fluoresce.

  • B. Candida albicans

    Candida causes moist, beefy red intertrigo with satellite lesions and no coral-red fluorescence.

  • C. Corynebacterium minutissimum (correct)

    Correct. Its porphyrin production causes the coral-red fluorescence.

  • D. Malassezia furfur

    Malassezia furfur causes pityriasis versicolor, which shows a yellow-gold fluorescence rather than coral red.

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 C, Corynebacterium minutissimum. Erythrasma is a superficial infection of the stratum corneum in intertriginous areas, and diabetes and obesity predispose to it.

Why is "Trichophyton rubrum" not the answer?

Trichophyton rubrum causes tinea cruris, which has an active raised edge and does not typically fluoresce.

Why is "Candida albicans" not the answer?

Candida causes moist, beefy red intertrigo with satellite lesions and no coral-red fluorescence.

Why is "Malassezia furfur" not the answer?

Malassezia furfur causes pityriasis versicolor, which shows a yellow-gold fluorescence rather than coral red.

What concept does this question test?

It tests Bacterial infections in Dermatology. The organism produces porphyrins that fluoresce coral red under Wood's light. Erythromycin is an effective treatment.

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 Bacterial 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.