Molluscum contagiosum is a common localized skin infection caused by the molluscum contagiosum virus that often occurs on the trunk, face and genitalia. It is more common in childhood as well as early adolescence, particularly in males, and is usually transmitted at this age via skin contact and autoinoculation. In adults, it is considered a sexually transmitted infection. Lesions appear as smooth, dome-shaped papules with central umbilication. In healthy patients, molluscum contagiosum is generally self-limiting and heals spontaneously after several months. However, in immunosuppressed individuals, lesions can be very large, widespread, and persistent. If treatment is indicated (e.g., for sexually transmitted molluscum contagiosum), cryotherapy with liquid nitrogen is usually the first treatment option.
- Sex: ♂ > ♀
- Age: most common in childhood (peak incidence < 5 years of age) and early adolescence
- More common in warm and humid climates or areas with poor hygiene
- Up to 20% of HIV-positive patients have symptomatic infection 
Epidemiological data refers to the US, unless otherwise specified.
- Pathogen: a DNA poxvirus (molluscum contagiosum virus)
- Risk factors: immunosuppression , active atopic dermatitis (in children), hot and humid climates, crowded living conditions 
Suspect AIDS if large, persistent, widespread lesions appear on an adult!
- Incubation period: 2–6 weeks
Physical examination: single or multiple lesions in healthy patients; especially widespread in immunocompromised patients 
- Nontender, skin-colored, pearly, dome-shaped papules with central umbilication (individual lesions may also be painful or pruritic)
- Usually 2–5 mm in diameter (giant lesions (> 15 mm) are encountered in immunocompromised patients)
- Papules contain a caseous plug.
- In children: face , trunk , and extremities; (e.g., axilla, antecubital and popliteal fossa)
- In adults: lower abdomen, groin, genitalia, and proximal thighs
- Chronic follicular conjunctivitis may occur as molluscum contagiosum viral particles spread into the conjunctiva of the eye (see “Molluscum contagiosum conjunctivitis”). 
- Clinical diagnosis 
- Seek out underlying etiologies (i.e., HIV testing) if lesions in adults and/or widespread
- A biopsy is usually not necessary, but consider in cases of immunosuppression, as the diagnostic differential is wide (see “Differential diagnosis” below).
- Localized to the epidermis
H&E-stained sections demonstrate the following
- Acanthosis (thickened epidermis)
- Cup-shaped invagination (the epidermis invaginates into the dermis)
- Molluscum bodies: keratinocytes with eosinophilic intracytoplasmic inclusion bodies containing viral particles
- Cutaneous cryptococcosis
- Cutaneous histoplasmosis
- Cutaneous aspergillosis
- Condyloma acuminatum
- Condylomata lata
- Verruca vulgaris
- Flat warts
The differential diagnoses listed here are not exhaustive.
Spontaneous remission of the lesions usually happens within a few months; thus, treatment is often unnecessary. 
Consider treatment for
- Sexually transmitted molluscum contagiosum
- Immunocompromised individuals
- Immunocompetent children upon parental request
- Cryotherapy; is often the first-line treatment for adolescents and adults as it is better tolerated than in children.
- Topical cantharidin
- Topical imiquimod have been used to successfully treat immunocompromised patients with refractory disease in some cases
- For immunocompromised individuals with severe and/or refractory disease
- Secondary bacterial infections
We list the most important complications. The selection is not exhaustive.