Molluscum contagiosum is caused by a common pox virus, producing lesions on the skin. In adults with healthy immune systems the lesions usually appear on the thigh or in the genital regions following sexual contact. However, in people with HIV they can spread widely, and they are particularly common on the face, where they can be spread by wet shaving with a blade. About 10 to 20% of people with symptomatic HIV infection develop molluscum contagiosum.

Symptoms and diagnosis

The viral infection causes small, pearly or waxy-looking flesh-coloured bumps about 2 to 4mm in diameter. Each dome-shaped bump has a hard, white central core, with or without a dent or 'umbilication' in the centre.

The infection is usually diagnosed by examination, although the bumps can sometimes be confused with warts caused by human papilloma virus (HPV) or certain fungal infections. To be certain of the diagnosis, a doctor will sometimes take a sample of one of the lesions for microscopic examination.

Treatment

Molluscum contagiosum may respond to the initiation of effective combination anti-HIV therapy. Otherwise, standard treatment consists of measures to remove the lesions. Removing the hard core appears to be essential for effective treatment.

The standard treatment is to spray each lesion with liquid nitrogen spray every one to two weeks. A trial at the Kobler Centre in London is testing whether applying podophyllin cream (Condyline / Warticon) to lesions that occur between liquid nitrogen applications improves the treatment.

Alternative treatments include chemicals such as trichloroacetic acid or other corrosive chemicals such as phenol, or cantharidin. Blistering usually occur within 24 hours, before the lesion can be scraped off. These treatments can be painful, and cannot be used on sensitive skin or on lesions close to the eyes.

It is important to use some sort of anti-bacterial ointment to prevent bacterial infection of the lesions. The anti-acne drugs tretinoin ointment (Vesanoid) or isotretinoin ointment or tablets (Roaccutane) can also help. These drugs are retinoids, which work by reducing the production of natural oils in the skin, encouraging the top layer to dry out and peel. The skin may become reddened and sore while these treatments are being used.

A third approach is surgical, where each lesions is scooped out using a blunt instrument. At some clinics the preferred treatment is to burn off the lesions using electricity. Both of these procedures are painful, so local anaesthesia and pain killers may be needed. There is also a significant risk of scarring.

Some men find that shaving with an electric razor or using a disinfectant scrub containing iodine inhibits the spread of molluscum to other parts of the beard area. Diluted tea tree oil is also reported by some to be effective in preventing the growth and spread of molluscum lesions, but this should not be applied undiluted to the skin.

There have been case reports of the successful treatment of molluscum, which had not responded to anti-HIV therapy, with cidofovir (Vistide). Cidofovir is a licensed anti-cytomegalovirus (CMV) drug, but it is active against a range of viruses including the pox virus that causes molluscum. It can be given intravenously, or as a 3% gel applied to the lesions. People who are taking combination antiretroviral therapy but still have molluscum lesions may benefit from cidofovir cream (Calista 2000). Side-effects include inflammation, a burning sensation and a loss of facial hair. Cidofovir cream is not commercially available.

Several case studies suggest that imiquimod cream (Aldara) may also have activity against molluscum lesions (Strauss 2001). Unlike cidofovir cream, imiquimod cream is commercially available as a treatment for genital warts.

Some people have reported good results using dinitrochlorobenzene (DNCB). However, injections of interferon alfa (IntronA / Roferon-A / Viraferon) do not appear to be effective.

The Phillips Molluscum Treatment System is a method that claims to be able to eliminate molluscum painlessly, safely and with a low chance of recurrence. However, there have been no published studies of the effectiveness or side-effects of this treatment, so it cannot be recommended at present.

Research

Calista (2000) reported that a topical cream containing 1% cidofovir was effective in clearing molluscum contagiosum in 4 people who had been taking combination antiretroviral therapy for over one year. Side effects included a burning sensation, inflammation and erosion of the skin.

Meadows reported the successful treatment of three cases of refractory molluscum contagiosum and giant, disfiguring lesions with cidofovir (intravenous therapy for four weeks, or topical therapy with 3% cidofovir gel).

Tappero enrolled 16 HIV-positive patients with molluscum contagiosum (MC) and a CD4 cell count below 200 cells/mm³in a study of interferon alfa (5 million units injected subcutaneously every day for 8 weeks). 15/16 participants completed the study. Overall, no decrease in the number of MC lesions was observed.

References

Calista D et al. Topical cidofovir for severe cutaneous human papillomavirus and molluscum contagiosum infections in patients with HIV/AIDS. A pilot study. Journal of the European Academy of Dermatology and Venereology 14(6): 484-488, 2000.

Davies EG et al. Topical cidofovir for severe molluscum contagiosum. Lancet 353(9169): 2042, 1999.

Horn CK et al. Resolution of severe molluscum contagiosum on effective antiretroviral therapy. British Journal of Dermatology 138(4): 715-717, 1998.

Meadows KP et al. Resolution of recalcitrant molluscum contagiosum virus lesions in human immunodeficiency virus-infected patients treated with cidofovir. Archives of Dermatology 133: 987-990, 1997.

Strauss RM et al. Successful treatment of molluscum contagiosum with topical imiquimod in a severely immunocompromised HIV-positive patient. International Journal of STDs and AIDS. 12(4): 264-266, 2001.

Tappero JW et al. Alpha interferon for severe HIV-associated molluscum contagiosum. Eighth International Conference on AIDS, Amsterdam, abstract PoB 3886, 1992.