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Molluscum contagiosum is clusters of pink, dome-shaped, smooth, waxy, or pearly and umbilicated papules 2 to 5 mm in diameter caused by molluscum contagiosum virus, a poxvirus. Diagnosis is based on clinical appearance. Treatment aims to prevent spread or remove cosmetically unacceptable lesions and can include mechanical methods (eg, curettage, cryosurgery) and topical irritants (eg, imiquimod, cantharidin, tretinoin).
Molluscum contagiosum virus commonly causes a localized chronic infection. Transmission is by direct contact; spread occurs by autoinoculation and via fomites (eg, towels, bath sponges) and bath water. Molluscum contagiosum is common among children. Adults acquire the infection via close skin-to-skin contact with an infected person (eg, sexual contact, wrestling). Patients with immunocompromise (eg, due to HIV/AIDS, corticosteroid use, chemotherapy) may develop a more widespread infection.
Symptoms and Signs
Molluscum contagiosum can appear anywhere on the skin except the palms and soles. Lesions consist of clusters of pink, dome-shaped, smooth, waxy, or pearly and umbilicated papules, usually 2 to 5 mm in diameter, which occur most commonly on the face, trunk, and extremities in children and on the pubis, penis, or vulva in adults. Lesions may grow to 10 to 15 mm in diameter, especially among patients with HIV infection and other immunodeficiencies. Lesions are usually not pruritic or painful and may be discovered only coincidentally during a physical examination. However, the lesions can become inflamed and itchy as the body fights off the virus.
Diagnosis
Diagnosis is based on clinical appearance; skin biopsy or smear of expressed material shows characteristic inclusion bodies but is necessary only when diagnosis is uncertain. Differential diagnosis includes folliculitis, milia, and warts (for lesions < 2 mm) and juvenile xanthogranuloma and Spitz nevus (for lesions > 2 mm).
Treatment
Most lesions spontaneously regress in 1 to 2 yr, but they can remain for 2 to 3 yr. Treatment is indicated for cosmetic reasons or for prevention of sexual spread. Options include curettage, cryosurgery, laser therapy, electrocautery, trichloroacetic acid (25 to 40% solution), cantharidin, podophyllin (in adults), tretinoin, tazarotene, and imiquimod 5% cream. Molluscum lesions within the orbital rim should be removed via gentle destruction by a skilled health care practitioner. Treatments that cause minimal pain (eg, tretinoin, imiquimod, tazarotene, cantharidin) are used first, especially in children. Curettage or liquid nitrogen can be used 40 to 60 min after application of a topical anesthetic such as eutectic mixture of local anesthetics (EMLA) or 4% lidocaine cream under an occlusive dressing. EMLA cream must be applied judiciously because it can cause systemic toxicity, especially in children. In adults, curettage is very effective but painful if done without anesthetic. Dermatologists often use combination therapy such as liquid nitrogen or cantharidin in the office and imiquimod cream or a retinoid cream at home. This form of therapy is typically successful, but resolution often takes 1 to 2 mo in some patients.
Nondermatologists should feel comfortable using imiquimod cream. The cream is applied at night, 1 drop to each molluscum lesion and rubbed in well, until the cream turns clear. In the morning, the treated area is washed with soap and water. The cream can be applied 3 to 7 times/wk. Lesions in the genital region and skinfolds easily become irritated. Lesions should be treated until they develop a scant amount of redness; treatment is then withheld to avoid weeping and crusting. Imiquimod should not be used within the orbital rim.
Cantharidin is safe and effective but can cause blistering. Cantharidin is applied in 1 small drop directly to the molluscum lesion. Areas that patients (especially children) may rub are covered with a bandage because contact with the fingers should be avoided. Cantharidin should not be applied to the face or near the eyes because blistering is unpredictable. If cantharidin comes into contact with the cornea, it can scar the cornea. Cantharidin should be washed off with soap and water in 6 h. Fewer than 15 lesions should be treated in one session, because infection may occur after application of cantharidin. Parents should be warned about blistering if their children are prescribed this drug.
Children should not be excluded from school or day care. However, their lesions should be covered to reduce the risk of spread.
Key Points
Last full review/revision September 2012 by James G. H. Dinulos, MD
Content last modified November 2012
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