Molluscum Contagiosum

Molluscum contagiosum is a common, benign, self-limiting viral skin infection caused by molluscum contagiosum virus, a member of the poxvirus family. It spreads by direct skin-to-skin contact or, indirectly, via fomites.

It produces small, discrete, umbilicated papules, mainly though not exclusively in young children. Lesions often persist for months, in some cases a year or more, before spontaneous resolution.

The essential clinical priorities are:

• confident clinical diagnosis, given the readily recognisable morphology
• parental reassurance about the benign, self-limiting natural history
• recognition of atypical contexts, such as significant immunocompromise or genital lesions in an adult, which warrant consideration of an alternative or additional underlying explanation

Pathophysiology and transmission

• The virus infects epidermal keratinocytes. Localised viral replication and cellular hypertrophy produce the umbilicated papule. In most immunocompetent individuals the virus stays confined to the epidermis, with no systemic viraemia or dissemination.
• Transmission is by direct skin contact, shared bathing or swimming facilities, and in some cases fomites such as shared towels or other items.
• Autoinoculation is common. Spread from an existing lesion to a new site by scratching or other direct contact explains the clustering of lesions and their tendency to spread locally.
• In sexually active adults, genital lesions typically reflect sexual transmission.
• In children, genital involvement more typically reflects autoinoculation from lesions elsewhere on the body, not sexual contact or abuse. This is a sensitive distinction that needs individualised clinical judgement according to age and overall context.
• In significantly immunocompromised individuals, particularly those with advanced HIV infection, lesions can be unusually extensive, large and treatment-resistant. This marks significant underlying immunosuppression. Consider HIV testing in an adult with this pattern when the diagnosis has not already been established.

• The defining feature is a small (typically 2 to 5 millimetres in diameter), discrete, firm, dome-shaped papule with a central umbilication (a small, central dimple or depression), typically flesh-coloured or pearly white.
• Lesions frequently occur in clusters and can arise at any cutaneous site, though they characteristically spare the palms and soles.
• Lesions are generally asymptomatic, though variable pruritus may occur.
• A surrounding eczematous dermatitis (molluscum dermatitis) develops around established lesions in a proportion of affected children. It is an immune-mediated reaction to the viral infection, not a separate dermatological condition.
• The natural history is prolonged but self-limiting. Individual lesions typically persist for approximately two to three months before spontaneous resolution.
• Ongoing autoinoculation produces new lesions as older ones resolve, so the overall course frequently extends to six months to a year, and occasionally longer, before all lesions clear.
• A localised inflammatory response around individual lesions (with erythema, swelling and sometimes discomfort) often precedes spontaneous resolution, though not universally. It is a favourable sign that the host immune system is beginning to clear the infection. It can alarm parents, and it should not be mistaken for secondary bacterial infection requiring antibiotic treatment.
• Extensive, numerous, large or treatment-resistant lesions, particularly in an adult, should prompt consideration of significant immunocompromise. Arrange further assessment, including HIV testing where this has not been previously established.

• Diagnosis is clinical, based on the readily recognisable appearance of small, discrete, umbilicated papules. A typical presentation needs no further investigation.
• Dermoscopy, where available and the diagnosis is uncertain, can confirm the central umbilication and surrounding vascular pattern. It is rarely required.
• If the diagnosis is genuinely uncertain, or an alternative is relevant, skin biopsy gives definitive histopathological confirmation. It shows Henderson-Paterson bodies (large, eosinophilic intracytoplasmic inclusion bodies). Rarely, in the immunocompromised patient, certain deep fungal infections can look superficially similar.
• Genital lesions in a child need careful, sensitive assessment of the overall context. Where indicated by the circumstances and any other concerning features, refer for formal safeguarding assessment, individualised to the case.
• Genital molluscum in a young child most commonly reflects autoinoculation rather than abuse. The possibility of abuse should not be dismissed without careful consideration of the full clinical context.

• Watchful waiting without active treatment is appropriate, standard management for the great majority of cases, given the benign, self-limiting natural history.
• The main component of management for most affected children is parental reassurance, with a clear explanation of the prolonged but self-resolving course.
• Active treatment is generally indicated for lesions causing significant discomfort or itching, lesions in a cosmetically sensitive location causing distress, or particularly problematic secondary eczematous dermatitis. It is also reasonable when the parent or patient prefers to treat rather than await spontaneous resolution of a frequently prolonged course.
• Individualise the decision between treatment and watchful waiting through shared, informed discussion with the family.
• Physical destructive methods are effective where active intervention is desired. They include cryotherapy (liquid nitrogen application) and curettage (physical removal of the lesion core). They cause discomfort, which matters particularly in young children, and may leave scars. Discuss their benefits and burdens against simple observation.
• Topical treatments, including potassium hydroxide solution and various other preparations, are generally less painful alternatives. Evidence for their effectiveness is variable. They are a reasonable option for families who want some active treatment while avoiding the more uncomfortable physical methods.
• Manage associated molluscum dermatitis with standard eczema measures (emollients and, where indicated, a mild topical corticosteroid), as under the general principles of eczema management. The dermatitis is generally expected to resolve after the molluscum lesions themselves.
• Advise against sharing towels or bathing items. Gently discourage scratching where practicable, recognising the difficulty in young children. These measures may help limit autoinoculation and spread.
• Advise limiting close, direct skin contact with other children during swimming or similar activities where practicable. Exclusion from school, childcare or swimming is not generally recommended, given the benign nature of the condition and its widespread presence in the childhood population.
• Clear parental education about the prolonged but self-limiting natural history, with reassurance about the cosmetic appearance and duration, underpins proportionate management of this extremely common, benign childhood viral skin infection.