Molluscum Contagiosum

MCV Basics - Poxy Papules Primer

• Etiology: Molluscum Contagiosum Virus (MCV), a DNA Poxvirus.
• Morphology: Firm, pearly, dome-shaped papules (2-5 mm) with central umbilication.
  • "Molluscum bodies" or Henderson-Paterson bodies: Eosinophilic intracytoplasmic inclusions.
• Transmission: Direct skin contact, fomites, autoinoculation.
• Commonly Affects: Children (especially atopic), immunocompromised (e.g., HIV), sexually active adults.
• Incubation: 2-7 weeks (up to 6 months).

⭐ MCV is a DNA poxvirus; MCV-1 is most common globally, while MCV-2 is more common in adults and often sexually transmitted.

Clinical Picture - Spot the Pearly Papules

• Morphology:
  • Firm, dome-shaped papules, 2-5 mm (giant >1 cm).
  • Pearly white, pink, or flesh-colored.
  • Key: Central umbilication (dimple).
  • Smooth, waxy surface.
  • Cheesy material (molluscum bodies) expressible.
  • Often grouped; linear spread from autoinoculation (Koebner phenomenon).
• Common Sites:
  • Children: Trunk, face, axillae, extremities.
  • Adults (often STI): Genitals, perineum, lower abdomen, inner thighs.
  • Immunocompromised (e.g., HIV): Widespread, numerous, larger, atypical (face common).
• Symptoms & Signs:
  • Often asymptomatic; may be pruritic.
  • Molluscum dermatitis: Eczema around lesions.
  • BOTE (Beginning Of The End): Spontaneous inflammation, signals resolution.

⭐ Characteristic lesions: firm, 2-5 mm, dome-shaped, pearly papules with central umbilication. Often pruritic.

Diagnosis & DDx - Confirming Contagiosum

• Clinical Diagnosis: Primarily based on characteristic pearly, dome-shaped, umbilicated papules (1-5 mm).
  • May be single or multiple.
  • Common sites: trunk, axillae, antecubital & popliteal fossae, anogenital region.
• Dermoscopy: Central pore/umbilication, whitish clods (molluscum bodies), surrounding crown vessels.
• Histopathology (rarely needed):

  ⭐ Diagnosis is usually clinical; histopathology shows pathognomonic Henderson-Paterson bodies (large eosinophilic intracytoplasmic inclusions in keratinocytes).

• Differential Diagnosis (DDx):
  • Viral warts (Verrucae)
  • Herpes simplex
  • Varicella
  • Folliculitis
  • Milia
  • Basal Cell Carcinoma (BCC) - esp. solitary lesions in adults
  • Cutaneous cryptococcosis/histoplasmosis (immunocompromised)

Management & Prevention - Clearing the Coast

• General Principles: Often self-limiting (resolve in 6-12 months, up to 4 years). Treatment for symptomatic relief, cosmesis, prevent autoinoculation/transmission.
• Conservative: Watchful waiting, especially in children.
• Physical Destruction:
  • Cryotherapy (liquid nitrogen): Painful, may scar.
  • Curettage: Effective, may scar, local anesthesia.
  • Laser (pulsed dye): Effective, expensive, less scarring.
• Chemical Agents:
  • Cantharidin (0.7%-0.9%): Vesicant, apply in-office, wash off in 2-6 hrs. Painless application, good for children. 📌 "Cantharidin Can Conquer Child's Concern"
  • Potassium hydroxide (5-10%): Home use, irritant.
  • Salicylic acid: Keratolytic.
  • Tretinoin (0.025%-0.1%): Irritant, for facial lesions.
• Immunomodulators:
  • Imiquimod (5% cream): Off-label, expensive, variable efficacy.
  • Cidofovir: Topical/intralesional for immunosuppressed.
• Prevention:
  • Avoid sharing towels, clothing, razors.
  • Cover lesions with clothing/watertight bandages.
  • Avoid scratching/picking.
  • No swimming if lesions not covered.

⭐ Often self-limiting (6-12 months); treatment aims to speed resolution, prevent spread, or for cosmetic reasons. Cantharidin (0.7%) is a common, painless office-based therapy for children.

High‑Yield Points - ⚡ Biggest Takeaways

• Caused by Molluscum Contagiosum Virus (MCV), a large DNA Poxvirus.
• Presents as characteristic pearly, dome-shaped, umbilicated papules (typically 2-5 mm).
• Histology reveals pathognomonic Henderson-Paterson bodies (intracytoplasmic eosinophilic inclusions).
• Transmitted by direct contact, fomites, or autoinoculation; highly prevalent in children.
• In HIV/immunocompromised states, expect numerous, larger, or persistent lesions.
• Often self-limiting in healthy individuals; treatments include cryotherapy, curettage, cantharidin.
• Common sites: trunk, axillae, anogenital region; notably spares palms and soles.