Common skin infections in children: Molluscum contagiosum and viral warts

In the first a two part series about children’s skin infections, Michael J Sladden and Graham A Johnston give an evidence based approach to the diagnosis and treatment of viral infections

Most children will have a skin infection at some time. Skin infections are a common reason for consultation, both in primary care and in dermatology practice. ¹²³ We review two common viral skin infections in children and describe their epidemiology, clinical features, and treatment, focusing on treatments with best evidence.

Molluscum contagiosum

Molluscum contagiosum is a common, benign, self limiting viral infection of the skin. It generally affects children and is caused by a human specific poxvirus. Infection is rare in children less than 1 year of age and typically occurs in the 2-5 year age group.⁴ Although the prevalence of molluscum contagiosum is not known, one of six Dutch children have visited their doctor for the condition.⁵

DOIA

Fig 1. Typical multiple dome shaped pearly or flesh coloured
papules of molluscum contagiosum, with a central depression (umbilication)

Infection follows autoinoculation or contact with affected people.⁶ The incubation period is from two weeks to six months. The condition is more common in young children and in children who swim, bathe together, and who are immunosuppressed. Little evidence supports the view that lesions (mollusca) are more common in children with atopic dermatitis.

Mollusca present as multiple dome shaped pearly or flesh coloured papules with a central depression (umbilication), which usually appear on the trunk and flexural areas (fig 1). They vary in size from 1 mm to 10 mm, with growth occurring over several weeks.⁴ In patients who are immunocompetent, lesions may persist for six to eight weeks. The mean duration is at least eight months when new lesions appear due to continuous autoinoculation. 6 Resolution is often preceded by inflammation. Uncomplicated lesions heal without scarring.

Whether doctors should treat molluscum contagiosum is controversial. As the condition is benign and typically resolves spontaneously, treatment is usually not necessary. Advocates of treatment state that intervention speeds resolution, reduces self inoculation and symptoms, limits spread, and prevents scarring. Often there is pressure from parents to treat their otherwise healthy children because of the stigma of visible lesions.⁷

Treatment

Many treatments for molluscum contagiosum have been reported, including physical destruction or manual extrusion of the lesions, cryotherapy, and curettage. Treatments are painful, and there is limited evidence that they are more effective than watchful waiting. One study found no difference in resolution of lesions after extrusion of the umbilicated core compared with destruction of the lesion using phenol, although treatment with phenol produced notably more scarring.6 Acidified nitrite cream has been reported as effective and painless.⁸ Topical imiquimod cream may be useful in widespread or recalcitrant mollusca, but it has not been tested in controlled trials.⁹

Fig 2. Cutaneous viral wart showing characteristic hyperkarotic
"warty" surface with capillary loops (black dots)

A Cochrane review is under way to evaluate treatments for molluscum contagiosum. Until there is clear evidence of safety and efficacy of active intervention, we recommend watchful waiting and reassurance of patients and parents.

Viral warts

Cutaneous viral warts are discrete benign epithelial proliferations caused by the human papillomavirus. Several types occur (box).

Viral warts are common.¹⁰ Prevalence increases during childhood, peaks in adolescence, and declines thereafter. ¹¹ In healthy children, warts resolve spontaneously; 93% of children with warts at age 11 showed resolution by age 16.¹² Resolution can be preceded by the appearance of blackened thrombosed capillary loops. Warts may be widespread and persistent in patients who are immunocompromised. The clinical appearance of warts depends on their location. The hands and feet are most commonly affected (fig 2).

Treatment

Although most warts resolve spontaneously within two years, some persist and become large and painful. For this reason many parents present their children for medical treatment. Treatment in children should be simple, cheap, effective, safe, and relatively painless.

Salicylic acid

Topical salicylic acid has been shown to be beneficial in treating viral warts. Data pooled from six randomised trials gave a cure rate of 75% in cases compared with 48% in controls (odds ratio 3.91, 95% confidence interval 2.40 to 6.36).^11,13 Preparations containing salicylic acid include creams, ointments, paints, gels, and colloids, with concentrations of the active ingredient varying from 11% to 50%. Salicylic acid breaks down hyperkeratotic skin but does irritate children’s skin. Topical salicylic acid should be regarded as first line treatment.

Cryotherapy

Systematic reviews show that cryotherapy is no better than topical salicylic acid.^11,13 Cryotherapy is best avoided in young children, as parents consider the side effects of pain, swelling, and blistering excessive for a benign self limiting condition. Aggressive cryotherapy scars children’s skin.

Other treatments

Although silver nitrate pencils and glutaraldehyde and formaldehyde preparations are licensed in the United Kingdom for treating warts, there is currently insufficient evidence of their benefit. Intralesional bleomycin, topical immunotherapy, photodynamic therapy, and pulsed dye laser treatment are best confined to research centres or resistant cases.

Michael J Sladden, specialist registrar
Email: m.sladden@doctors.org.uk

Graham A Johnston, consultant, Department of Dermatology, Leicester Royal Infirmary, University Hospitals of Leicester NHS Trust, Leicester, LE1 5WW


studentBMJ 2005;13:133-176 April ISSN 0966-6494

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