Common Cutaneous Viral Infections
Cutaneous viral infections are classified by the responsible virus family. Diagnosis is often clinical, but definitive testing includes PCR or Tzanck smear.
Key Viral Dermatoses
| Condition | Virus | Clinical Key |
|---|---|---|
| Molluscum Contagiosum | Poxvirus | Umbilicated, flesh-colored papules. |
| Herpes Simplex (HSV) | HSV-1 / HSV-2 | Grouped vesicles on an erythematous base. |
| Verruca Vulgaris | HPV | Hyperkeratotic papules with thrombosed capillaries. |
| Varicella Zoster | VZV | Dermatomal distribution (Shingles). |
Clinical Pearls & Exam Focus
- Tzanck Smear: Used for HSV/VZV—look for multinucleated giant cells.
- Molluscum: If generalized/widespread in adults, consider underlying HIV or immunosuppression.
- HPV: Look for “black dots” (thrombosed capillaries) on scraping—a classic board feature of warts.
High-Yield Exam Pearl:
- Eczema Herpeticum: A serious HSV infection in patients with underlying atopic dermatitis; presents as monomorphic “punched-out” erosions. Treat immediately with Acyclovir.
- Herpes Zoster: The “dermatomal” clue is absolute. If it involves the tip of the nose (Hutchinson’s sign), look for ophthalmic zoster involvement.