Molluscum Contagiosum

Key Features

• Caused by a poxvirus

• The lesions are autoinoculable and spread by wet skin-to-skin contact

• In sexually active individuals, lesions may be confined to the penis, pubis, and inner thighs and are considered a sexually transmitted infection

• Common in AIDS patients

  • Usually with a helper T cell count < 100/mcL

  • Extensive lesions tend to develop over the face and neck as well as in the genital area

  • Lesions are difficult to eradicate unless immunity improves, in which case spontaneous clearing may occur

Clinical Findings

• Presents as single or multiple, dome-shaped, waxy papules 2–5 mm in diameter that are umbilicated

• Lesions at first are firm, solid, and flesh colored but on reaching maturity become soft, whitish, or pearly gray and may suppurate

• The principal sites are the face, lower abdomen, and genitals

• Individual lesions persist for about 2 months

Diagnosis

• Clinical; based on the distinctive central umbilication of the dome-shaped lesion

• Differential diagnosis

  • Warts

  • Varicella (chickenpox)

  • Basal cell carcinoma

  • Lichen planus

  • Smallpox

  • Cutaneous cryptococcosis (in AIDS)

Treatment

• The best treatment is by curettage or applications of liquid nitrogen as for warts but more briefly

• When lesions are frozen, the central umbilication often becomes more apparent

• Light electrosurgery with a fine needle is also effective

• Cantharidin (applied in the office and then washed off by the patient 4 hours later) is a safe and effective option

• Other treatment options

  • Potassium hydroxide 10% solution applied twice daily until lesions clear

  • Salicylic acid

  • Podophyllotoxin

  • Tretinoin

  • Imiquimod

  • Pulsed dye laser

  • Comedone extractor or currette