Molluscum contagiosum

Viral skin infection caused by a pox virus. The infection is most common in children of school age, particularly under the age of eight years. It is transmitted by direct contact with infected persons, and it is still in dispute as to whether the infection can be contracted by indirect contagion via contaminated material such as towels. In the affected subject, the infection spreads by autoinoculation.

Signs and symptoms

The mollusca present as hemispherical protrusions, navel-like at the centre, with a smooth surface. The lesions are usually small, a few millimetres in diameter. The infection sometimes presents with larger components up to several centimetres in diameter (giant forms). The number varies from one or a few components up to dozens in the diffuse forms. The mollusca tend to be more numerous in children with atopic dermatitis. They are located on the face and neck in particular, but may also affect the trunk and scalp. On the scalp, if onset is during the first months of life, maternal contagion during labour is suspected. Genital involvement, common in adults, in children must entail the ruling out of sexual abuse. Superinfection is one of the possible complications.

In addition, molluscum contagiosum may spontaneously lead to inflammatory processes. The lesion becomes erythematous-oedematous and in this case it is called inflamed molluscum contagiosum. It is a cell-mediated immunoreaction which sometimes induces the regression of all the components, and for this reason does not require any treatment. Molluscum dermatitis is an eczematous inflammatory reaction that may be perilesional, when a single molluscum is involved, or may be manifested elsewhere. It is usually accompanied by pruritus, and scratching encourages spreading of the infection due to autoinoculation. In these cases it is advisable to control the inflammation with topical steroids and emollients. Rarer is the Gianotti-Crosti syndrome-like reaction encouraged by the presence of inflamed mollusca, and characterised by the appearance of multiple papular lesions which appear at a distance, on elbows and knees, together with pruritus. It is considered a dermatophytic reaction, inflammatory in nature, and so the reaction should be distinguished from the spreading of the infection. Dermoscopy is useful for diagnosis as the papules of the Gianotti-Crosti syndrome-like reaction do not show the typical aspects of molluscum. The use of topical steroids is indicated.

The duration of the infection varies; it may heal spontaneously within two years, although in some cases more slowly.

Treatment

There is no therapy with certain efficacy. In some cases, especially if the lesions are multiple and recurring, only supervision may be provided although parents often ask for the lesions to be removed. Curettage is painful and sometimes successive sessions are difficult to perform due to poor compliance by the child. In addition, treatment may leave dyschromic sequelae or scarring. The same applies for CO2 laser. Alternatively topical irritant agents such as 5% or 10% potassium hydroxide may be used, which the parents administer at home, making sure to treat only a few lesions at a time. To ensure therapeutic compliance, it is essential to explain to the parents the various treatment options, the risks and the limitations of the different treatments. Recurrences are reported in 35% of the subjects treated.

The infection is not a mandatory notifiable disease and affected children are not isolated and may remain in the community.

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