Tzanck Smear
The Tzanck smear is a rapid, inexpensive cytodiagnostic tool used to evaluate vesiculobullous lesions. It is primarily used to identify viral infections caused by the Herpesviridae family.
Technique & Interpretation
- Procedure: The base of a fresh, unroofed vesicle is scraped with a scalpel, transferred to a slide, and stained with Giemsa, Wright, or Methylene blue stain.
- Positive Result: The presence of multinucleated giant cells (syncytia) is diagnostic of a herpes virus infection.
Diagnostic Applications
| Condition | Tzanck Finding |
|---|---|
| Herpes Simplex (HSV) | Multinucleated giant cells + Acantholysis. |
| Varicella-Zoster (VZV) | Multinucleated giant cells. |
| Pemphigus Vulgaris | Isolated acantholytic cells (Tzanck cells) without giant cells. |
High-Yield Exam Pearl:
- Viral Distinction: While the Tzanck smear identifies that a herpes virus is present, it cannot distinguish between HSV-1, HSV-2, or VZV. Immunofluorescence or PCR is required for definitive viral subtyping.
- Utility: It is falling out of favor compared to PCR, which is significantly more sensitive and specific, but it remains a classic “point-of-care” diagnostic question on board examinations.