Oxford Handbook of Genitourinary Medicine, HIV, and Sexual
Health (2 edn)
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Introduction
First described in 1817. Viral origin discovered by Juliusburg in 1905.
Aetiology
Molluscum contagiosum virus (MCV), genus Molluscipoxvirus, a poxvirus.
A benign self-limiting skin infection caused by a large DNA virus replicating in cytoplasm of epithelial cells. There are four major subtypes: MCV1 (↑ in children) and MCV2 (↑ in adults and those with HIV infection) are the most common, and two further subtypes (MCV3 and MCV4) are described although these remain rare. Humans are the only natural host.
Epidemiology and transmission
Worldwide, more common in warm climates. Linked to poor hygiene and overcrowding. Equal sex distribution. Transmitted by direct skin-to-skin contact. Microscopic abrasions (trauma) and a warm moist environment facilitate transmission. The period of infectivity and viral shedding is thought to be equal to the duration of lesions.
Both sexual and non-sexual spread occurs. The latter is more common especially in:
pre-adolescent children (17% in those aged <15 years)
individuals with impaired cellular immunity
sports involving skin-to-skin contact
those using gyms, swimming pools, and saunas (including fomites, e.g. shared towels)
If sexually acquired, lesions are usually found around the anogenital area and in:
sexually active adults aged 20–29 years
those with a history or presence of other STIs
those whose partner has molluscum contagiosum
There are no documented cases of maternal–fetal transmission. HIV testing is recommended in those presenting with facial lesions.
Clinical features
Incubation period usually 2–12 weeks, up to 6 months. Smooth pearly coloured umbilicated lesions growing over several weeks to a diameter of 2–6mm, occasionally larger (Plate 14). In adults, when sexually acquired, found in pubic region, thighs, buttocks, lower abdomen, and less commonly external genitalia sparing mucous membranes. Usually up to 10–20 lesions unless immunosuppressed. May appear during pregnancy and generally resolve after delivery. Typically asymptomatic but may cause pruritus (10% develop dermatitis around lesions), leading to auto-inoculation through excoriation. In children lesions are characteristically found on face, upper limbs, and trunk but 10–50% have genital lesions.
Spontaneous resolution within 2–3 months is common, but recurrences occur in 15–35% over 8–24 months.
Diagnosis
Characteristic appearance
Histology: enlarged epithelial cells with intra-cytoplasmic molluscum bodies.
Molluscum contagiosum is a viral infection spread by skin-to-skin contact. If lesions appear around the genitals they have probably been sexually transmitted.
Lesions usually appear after an incubation period of 3–12 weeks (although this can be longer) and usually disappear spontaneously within 2–3 months. Clearance depends on the body mounting a suitable immunological response against the causative poxvirus.
As molluscum resolves spontaneously, treatment is offered for cosmetic purposes only. Generally people with genital lesions want them cleared up as soon as possible.
The usual treatment is by cryotherapy, but curettage, diathermy, and piercing with an orange stick followed by applyication of iodine or phenol have also been used. There are limited data on podophyllotoxin cream and imiquimod cream (currently unlicensed).
33% of people will experience recurrences over the next 1–2 years.
Management
As molluscum contagiosum frequently resolves without treatment, the benefits of treating lesions must be balanced against the possible risk of post-treatment scarring.
Treatment options include:
curettage, cryotherapy, electrocautery, puncture with sharpened orange stick dipped in 80% phenol
imiquimod cream 5%
podophyllotoxin 0.5% (reported but very limited data on efficacy)
oral cimetidine (conflicting results on efficacy)
adapalene.
Partner notification
Unnecessary. No evidence that treating partner prevents reinfection.
HIV infection
Molluscum contagiosum is found in up to 20% of those with
HIV. Lesions may become widespread in those with low CD4 counts and high
viral loads (commonly affecting the face) and hypertrophic. Use of HAART may
lead to resolution of lesions, but conversely may present following an
immune reconstitution inflammatory syndrome (IRIS) (
Chapter 53, Immune reconstitution p. 592)
