Molluscum contagiosum

Molluscum contagiosum (moll-us-cum con-tag-ee-oh-sum) is a skin infection that is caused by a virus called the molluscum contagiosum virus. There are four types of molluscum contagiosum virus, MCV-1 to -4; MCV-1 is the most prevalent and MCV-2 is seen usually in adults and often sexually transmitted.

It appears as raised, pearl-like bumps with a central core or plug of white, cheesy or waxy material on the skin or occasionally in the mucous membranes (soft moist body parts like the inside of the mouth and nose). This common viral disease has a higher incidence in children, sexually active adults, and those who are immunodeficient. Molluscum contagiosum virus does not infect animals and it is most common in children aged one to ten years old. Molluscum contagiosum can affect any area of the skin but is most common on the body, arms, and legs.  In adults, the lesions are commonly seen on the genitals, abdomen, and inner thigh.

The virus can spread through any skin-to-skin contact and through objects that have the virus on them, such as towels, clothing, or toys. The virus can spread from one part of the body to another or to other people. Molluscum contagiosum is contagious until the bumps are gone which, if untreated, may be up to 6 months or longer. Once a person is infected usually takes 2-7 weeks for bumps to appear but the virus can incubate for up to 6 months.

Signs, symptoms and diagnosis

Diagnosis is made based on the appearance of the bumps as the virus cannot routinely be cultured. The diagnosis can be confirmed by excisional biopsy (removal of one or more of the bumps to be examined under a microscope.)

The lesions are the same colour as the patient’s skin, dome-shaped, and pearly in appearance. They are about 1–5 millimetres in diameter, with a dimpled centre. They are usually not painful, but they may itch or become irritated. Picking or scratching the bumps may lead to bleeding, further infection or scarring. In about 10% of the cases, eczema develops around the lesions.

The viral infection is limited to a localized area on the topmost layer of the skin. Once the head of the lesion with its central waxy core which contains the virus has been destroyed, the infection is gone. The virus may spread to other skin areas through a process called autoinoculation. Children are particularly susceptible to autoinoculation, and may have multiple clusters of lesions called crops. The bumps may occur in lines where the person has scratched.

Causes, incidence, and risk factors

Molluscum contagiosum is caused by a virus that is a member of the poxvirus family. You can get the infection in a number of different ways. This is a common infection in children and occurs when a child comes into direct contact with a lesion. It is frequently seen on the face, neck, armpit, arms, and hands but may occur anywhere on the body except the palms and soles of the feet. The virus also spreads by sexual contact. Early lesions on the genitalia may be mistaken for herpes or warts but, unlike herpes, these lesions are painless. Persons with a weakened immune system (due to conditions such as AIDS) may have a rapidly worse case of molluscum contagiosum.

Treatment

Treatment is often unnecessary depending on the location and number of lesions, and no single approach has been convincingly shown to be effective. It should also be noted that treatments causing the skin on or near the lesions to rupture may spread the infection further, much the same as scratching does.

Cryotherapy kills infected cells by "freezing" them with a pressurized liquid spray, usually liquid nitrogen or nitrous oxide.

Astringents (drying agents) applied to the surface of molluscum lesions destroy successive layers of the skin. These can be over the counter preparations or stronger ones applied by a healthcare professional.

Other topical treatments have also been found to be effective:

• Australian lemon myrtle
• 10% benzoyl peroxide
• cantharidin
• tea tree oil
• salicylic acid
• tretinoin cream ("Retin-A 0.025%")

Doctors occasionally prescribe imiquimod, a form of immunotherapy. Immunotherapy triggers the immune system to fight the virus causing the skin growth. Imiquimod is applied 3 times per week, left on the skin for 6 to 10 hours, and washed off. A cure may take from 4 to 16 weeks. 

Surgical treatments include cryosurgery, in which liquid nitrogen is used to freeze and destroy lesions, as well as scraping them off with a curette. Application of liquid nitrogen may cause painful burning or stinging at the treated site, which may persist for a few minutes after the treatment. This can also cause scarring or permanent white marks in the treated area. With liquid nitrogen, a blister may form at the treatment site, but it will heal in two to four weeks.

Pulsed dye laser therapy for molluscum contagiosum may be the treatment of choice for multiple lesions and has been documented with excellent results. The therapy was well tolerated, without scars or pigment anomalies. The lesions resolved without scarring at 2 weeks. The pulsed dye laser is quick and efficient, but its expense makes it less cost effective than other options. Also, not all dermatology offices have the required laser.

Most cases of molluscum will clear up naturally within two years (usually within nine months). So long as the skin growths are present, there is a possibility of transmitting the infection to another person. When the growths are gone, the possibility for spreading the infection is ended. Unlike herpes viruses, which can remain inactive in the body for months or years before reappearing, molluscum contagiosum does not remain in the body when the growths are gone from the skin and will not reappear on their own. However, there is no permanent immunity to the virus, and it is possible to become infected again.

If left untreated, molluscum growth can reach sizes as large as a pea or a marble. Spontaneous resolution of these lesions can occur, but will leave a large crater. As many treatment options are available, prognosis for minimal scarring is best if treatment is started while lesions are small.

References

http://en.wikipedia.org/wiki/Molluscum_contagiosum

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001829/

 

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