Molluscum Contagiosum in Children

Molluscum contagiosum is a benign viral skin infection of children caused by a poxvirus, producing discrete, pearly, umbilicated papules that resolve spontaneously.

• It occurs mainly in children aged 1 to 10 years and is spread by skin contact, fomites (towels, toys, baths) and swimming pools. Autoinoculation spreads lesions.
• It is commoner and more extensive in atopic dermatitis and in immunocompromised children, including those with HIV.
• Incubation is 2 to 7 weeks. Lesions resolve spontaneously within 6 to 18 months, occasionally up to 4 years.
• Extensive or giant lesions in older children or adults should prompt consideration of HIV.

Lesions are distinctive.

• Firm, dome-shaped, flesh-coloured or pearly papules 2 to 5 mm in diameter, with central umbilication and a cheesy core.
• Single or clustered, often in groups on the trunk, axillae, flexures, face and limbs.
• Usually asymptomatic. Some are itchy.
• Surrounding eczematous reaction (molluscum dermatitis) in some children.
• Inflammation, redness and swelling of a lesion before it resolves (the "beginning of the end" sign).
• Secondary bacterial infection with scratching.
• Differential diagnosis: warts, milia, folliculitis, varicella, papular eczema, Gianotti-Crosti syndrome, cryptococcosis (in HIV), molluscum-like lesions of other infections, and basal cell carcinoma (rare).
• Complications: secondary infection, eczema flare, scarring, conjunctivitis or keratitis (eyelid lesions), and psychosocial impact.

Diagnosis is clinical.

• Typical appearance on inspection, with dermoscopy showing central pore and surrounding vessels.
• Express the core to identify molluscum bodies on microscopy if in doubt.
• Biopsy for atypical or giant lesions.
• Consider HIV testing in extensive, giant or persistent lesions, or when other features suggest immunodeficiency.

Observation is the preferred approach in most children.

• Supportive: reassure that lesions resolve without scarring. Avoid scratching and shaving over lesions, cover with clothing, do not share towels, and treat any atopic dermatitis. Children can attend school and swim, with lesions covered.
• Pharmacological, if treatment is wanted: potassium hydroxide 5 to 10 percent solution applied once or twice daily to lesions until inflammation develops. Topical cantharidin 0.7 percent applied by a clinician and washed off after 2 to 6 hours. Topical salicylic acid 12 to 16 percent paint at night (avoid on face). Topical imiquimod is not used because it has not been shown to work.
• Treat molluscum dermatitis with mild topical corticosteroid (hydrocortisone 1 percent twice daily for 5 to 7 days) and emollients.
• Secondary infection: topical fusidic acid 2 percent three times daily for 5 to 7 days or flucloxacillin 12.5 to 25 mg/kg four times daily orally.
• Procedures: curettage, cryotherapy with liquid nitrogen (short freeze, 5 to 10 seconds), or pricking and expression of the core, with topical anaesthetic (lidocaine-prilocaine cream) beforehand. Eyelid lesions need ophthalmology review.
• Special groups: children with HIV need antiretroviral therapy, which clears lesions. Extensive disease in an immunocompromised child needs specialist treatment.
• Red flags: eyelid lesions with red eye, widespread or giant lesions, rapid spread, secondary infection, and persistence beyond 2 years.
• Follow-up: review in 3 to 6 months if untreated. Review earlier if inflamed, infected or spreading.