• Clinical science

Molluscum contagiosum

Abstract

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.

Epidemiology

  • Sex: >
  • Age: most common in childhood (peak incidence < 5 years of age) and early adolescence
  • Prevalence
    • More common in warm and humid climates or areas with poor hygiene
    • About 1% of total skin disorders in the US
    • Up to 18% of HIV-positive patients and up to 33% if CD4 cell count is < 100 cells/μL

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Pathogen:: a DNA poxvirus (molluscum contagiosum virus)
  • Transmission:
    • Direct skin contact (contact sports, sexually transmitted in sexually active adolescents and adults)
    • Autoinoculation (scratching or touching lesion, e.g., while shaving)
    • Fomites (e.g., on bath sponges/towels)
  • 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!

References:[1][2]

Clinical features

  • Incubation period: 2–6 weeks
  • Physical examination: single or multiple lesions in healthy patients; especially widespread in immunocompromised patients
    • Nontender, flesh-colored, pearly, dome-shaped papules with central umbilication
      • Individual lesions may also be painful or pruritic.
    • Usually 2–5 mm in diameter
    • Papules contain a caseous plug.
  • Predilection sites:
    • 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.

References:[1][3][4]

Diagnostics

  • 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).

References:[3]

Pathology

Histology

References:[1][3]

Differential diagnoses

References:[1][3]

The differential diagnoses listed here are not exhaustive.

Treatment

  • Spontaneous remission usually happens within 6–9 months (thus treatment often unnecessary).
  • Consider treatment for sexually transmitted cases, immunocompromised individuals, and/or to reduce autoinoculation or transmission.
  • Cryotherapy; is often the first-line treatment for adolescents and adults as it is better tolerated than in children.
  • Curettage
  • Topical cantharidin
  • Podophyllotoxin
  • Topical imiquimod may be used to successfully treat immunocompromised patients with refractory disease, along with antiretrovirals in HIV-positive patients.

References:[1][3]

Complications

  • Scarring
  • Hypopigmentation
  • Secondary bacterial infections

References:[3]

We list the most important complications. The selection is not exhaustive.