Molluscum Contagiosum

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 of molluscum contagiosum 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 Diagnosis Folliculitis is an infection of hair follicles. Diagnosis is clinical. Treatment for most cases of bacterial folliculitis is with topical mupirocin or clindamycin. (See also Overview of Bacterial... read more , milia Cutaneous Cysts Epidermal inclusion cysts are the most common cutaneous cysts. Milia are small epidermal inclusion cysts. Pilar cysts are usually on the scalp and may be familial. Benign cutaneous cysts are... read more , and warts Warts Warts are common, benign, epidermal lesions caused by human papillomavirus infection. They can appear anywhere on the body in a variety of morphologies. Diagnosis is by examination. Warts are... read more (for lesions < 2 mm) and juvenile xanthogranuloma and Spitz nevus (for lesions > 2 mm).

Most lesions spontaneously regress in 1 to 2 years, but they can remain for 2 to 3 years.

Treatment of molluscum contagiosum is indicated for cosmetic reasons or for prevention of spread. Options include curettage, cryosurgery, laser therapy, electrocautery, trichloroacetic acid (25 to 40% solution), cantharidin, podophyllotoxin (podofilox) in adults, tretinoin, and tazarotene. Some clinicians use salicylic acid, but others consider it too irritating for many body areas where molluscum occurs. Similar concerns exist with use of potassium hydroxide (KOH). Small studies suggest that ingenol mebutate gel, a cytotoxic agent used to treat actinic keratoses, may be effective (1 Treatment references Molluscum contagiosum is characterized by 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... read more ). Molluscum lesions within the orbital rim should be removed via gentle destruction by a skilled clinician. Lesions may be gently squeezed with a forceps to remove the central core. Treatments that cause minimal pain (eg, tretinoin, tazarotene, cantharidin) are used first, especially in children. Imiquimod is usually not recommended.

Curettage or liquid nitrogen can be used 40 to 60 minutes after application of a topical anesthetic such as EMLA (lidocaine/prilocaine) cream 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.

Cantharidin is safe and effective but can cause blistering. It 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 cause scarring. Cantharidin should be washed off with soap and water in 6 hours. 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 irritant.

Other treatments include intralesional injection (eg, with Candida antigen or occasionally interferon alpha; 2 Treatment references Molluscum contagiosum is characterized by 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... read more ) and photodynamic therapy. Antiviral and immunomodulatory medications have been more successful in patients infected with HIV (3 Treatment references Molluscum contagiosum is characterized by 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... read more ).

Dermatologists often use combination therapy such as liquid nitrogen or cantharidin in the office or a retinoid cream at home. This form of therapy is typically successful, but resolution often takes 1 to 2 months in some patients.

Children should not be excluded from school or day care. However, their lesions should be covered to reduce the risk of spread.