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Pathology · single question

To definitively diagnose pemphigus vulgaris and distinguish it from herpetic gingivostomatitis, the best test is:

  1. Biopsy with direct immunofluorescence
  2. A Tzanck smear alone
  3. A complete blood count
  4. An empirical trial of acyclovir
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Correct answer: A. Biopsy with direct immunofluorescence

  • A. Correct. Biopsy with DIF reveals the intercellular IgG of pemphigus and separates it from a viral infection.
  • B. Incorrect. A Tzanck smear can suggest viral acantholysis but is not specific enough to confirm pemphigus.
  • C. Incorrect. A CBC does not diagnose either condition.
  • D. Incorrect. A drug trial is not a diagnostic test and delays definitive diagnosis.

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