Molluscum Contagiosum

Definition

Molluscum contagiosum is a benign, self-limited viral infection of the skin and occasionally mucous membranes caused by the Molluscum contagiosum virus (a poxvirus), characterized by small, firm, umbilicated papules.

Epidemiology

• Common in children, sexually active adults, and immunocompromised individuals (especially those with HIV).
• Transmitted through direct skin-to-skin contact, autoinoculation, or contact with contaminated fomites (e.g., towels, razors).
• In adults, often sexually transmitted and localized to the genital area.
• Higher incidence in warm, humid climates and in individuals with atopic dermatitis or skin barrier defects.
• Incubation period ranges from 2 weeks to 6 months.

Etiology

• Caused by the Molluscum contagiosum virus (MCV), a member of the Poxviridae family.
• Four subtypes identified (MCV-1 to MCV-4); MCV-1 is most common in children, MCV-2 more common in adults.
• Spread via direct contact, sexual transmission, or fomites.
• Risk factors: immunosuppression (HIV, transplant), atopic dermatitis, poor hygiene, crowded living conditions.

Pathophysiology

• The virus infects epidermal keratinocytes, leading to localized proliferation and formation of dome-shaped papules.
• Infected cells develop large intracytoplasmic inclusion bodies (Henderson-Patterson bodies).
• Host immune response eventually leads to resolution, but immunity is incomplete, allowing reinfection.
• Lesions are limited to the epidermis and do not cause systemic illness.