VIRUS · Enveloped dsDNA herpesvirus (α-herpesvirus)
Herpes Simplex Virus (HSV-1/HSV-2)
Herpes Simplex Virus — Tzanck smear (multinucleated giant cells)
Stain: Tzanck (Giemsa/Wright) smear of vesicle baseMorphology: Acantholytic keratinocytes and multinucleated giant cells with molded nuclei and ground-glass chromatin (Cowdry A intranuclear inclusions)Yield: HIGHDifficulty: MEDIUM
Image: Wikimedia Commons (CC BY-SA 4.0)
Key facts
**Pathogenesis**: HSV-1 typically oral, HSV-2 typically genital. Establishes latency in sensory ganglia (trigeminal for HSV-1, sacral for HSV-2) and reactivates with stress, UV, immunosuppression. **Diagnostic clue**: Tzanck smear shows multinucleated giant cells (positive in HSV, VZV — not specific). PCR of vesicle fluid or CSF is gold standard. Temporal lobe involvement on MRI suggests HSV encephalitis. **Virulence**: Latency via LAT transcripts; thymidine kinase target of antivirals.
Boards buzzwords
- multinucleated giant cells
- Cowdry A inclusions
- molded nuclei
- temporal lobe encephalitis
- vesicles on erythematous base
- trigeminal/sacral ganglion latency
Associated diseases
- Gingivostomatitis / herpes labialis
- Genital herpes
- Herpetic whitlow
- Keratoconjunctivitis (dendritic ulcers — avoid steroids)
- HSV temporal lobe encephalitis (#1 sporadic encephalitis in adults)
- Neonatal herpes
- Eczema herpeticum
Treatment
Acyclovir, valacyclovir, or famciclovir for mucocutaneous disease; IV acyclovir for HSV encephalitis, neonatal disease, or disseminated; foscarnet for acyclovir-resistant (TK-deficient) strains
