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Molluscum contagiosum

Molluscum contagiosum (MC) is a viral infection of the skin or occasionally of the mucous membranes. MC has no animal reservoir, infecting only humans, as did smallpox. However, there are different pox viruses that infect many other mammals. The infecting human MC virus is a DNA poxvirus called the molluscum contagiosum virus (MCV). There are 4 types of MCV, MCV-1 to -4, with MCV-1 being the most prevalent and MCV-2 seen usually in adults and often sexually transmitted. About one in six young are infected at some time with MC. The infection is most common in children aged one to ten years old. MC affects any area of the skin but is most common on the body, arms, and legs. It is spread through direct contact or shared articles of clothing (including towels).

In adults, molluscum infections are often sexually transmitted and usually affect the genitals, lower abdomen, buttocks, and inner thighs. In rare cases, molluscum infections are also found on the lips, mouth, and eyelids.

The time from infection to the appearance of lesions ranges from 2 week to 6 months, with an average incubation period of 6 weeks. Diagnosis is made on the clinical appearance; the virus cannot routinely be cultured.

Symptoms

Molluscum contagiosum lesions are flesh-colored, dome-shaped, and pearly in appearance. They are often 1-5 millimeters in diameter, with a dimpled center. They are generally not painful, but they may itch or become irritated. Picking or scratching the bumps may lead to further infection or scarring. In about 10% of the cases, eczema develops around the lesions. They may occasionally be complicated by secondary bacterial infections.

The central waxy core contains the virus. In a process called autoinoculation, the virus may spread to neighboring skin areas. Children are particularly susceptible to auto-inoculation, and may have widespread clusters of lesions.

Treatments

Individual molluscum lesions may go away on their own and are reported as lasting generally from 6 to 8 weeks, to 2 or 3 months. However via autoinoculation, the disease may propagate and so an outbreak generally lasts longer with mean durations variously reported as 8 months, to about 18 months, and with a range of durations from 6 months to 5 years.

Treatment is often unnecessary depending on the location and number of lesions, with no single approach shown to be convincingly effective. Nonetheless, treatment may be sought after for the following reasons:

Medical issues including:

Bleeding
Secondary infections
Itching and discomfort
Potential scarring
Chronic keratoconjunctivitis

Social reasons

Cosmetic
Embarrassment
Fear of transmission to others
Social exclusion

Many health professionals recommend treating bumps located in the genital area to prevent them from spreading. The virus lives only in the skin and once the growths are gone, the virus is gone and the virus cannot be spread to others. Molluscum contagiosum is not like herpes viruses, which can remain dormant in the body for long periods and then reappear. Thus, when treatment has resulted in elimination of all the bumps, the infection has been effectively cured and will not reappear unless the patient is reinfected. In practice, it may not be easy to see all of the molluscum contagiosum bumps. Even though they appear to be gone, there may be some that were overlooked. If this is the case, one may develop new bumps by autoinoculation, despite their apparent absence.

Betadine

There are a few treatment options that can be done at home. Betadine surgical scrub can be gently scrubbed on the infected area for 5 minutes daily until the lesions resolve (this is not recommended for those allergic to iodine or betadine). However, the ability of iodine to penetrate intact skin is poor, and without a pin prick or needle stick into each molluscum lesion this method does not work well. Do not use on broken skin.

Astringents

Astringent chemicals applied to the surface of molluscum lesions to destroy successive layers of the skin include trichloroacetic acid, podophyllin resin, potassium hydroxide, and cantharidin.

Australian lemon myrtle

A 2004 study demonstrated over 90% reduction in the number of lesions in 9 out of 16 children treated with 10% strength solution of essential oil of Australian lemon myrtle (Backhousia citriodora). However the oil may irritate normal skin at concentrations of 1%.

Tea tree oil

Another essential oil, tea tree oil is reported to at least reduce growth and spread of lesions when used in dilute form.

Over-the-counter substances

For mild cases, over-the-counter wart medicines, such as salicylic acid may shorten infection duration. Daily topical application of tretinoin cream ("Retin-A 0.025%") may also trigger resolution. These treatments require several months for the infection to clear, and are often associated with intense inflammation and possibly discomfort.

Imiquimod

Doctors occasionally prescribe Imiquimod, the optimum schedule for its use has yet to be established. Imiquimod is a form of immunotherapy. Immunotherapy triggers your 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 course may last from 4 to 16 weeks. Small studies have indicated that it is successful about 80% of the time

Systemic treatments

Cimetidine (however, double blind placebo studies seem to refute this), Griseofulvin (single case, anecdotal evidence) and Methisazone have seen some use.

Non-medicinal treatment

The viral infection is limited to a localized area on the topmost layer of the epidermis, specifically, the head of the lesion. Once the virus containing head of the lesion has been destroyed, the infection is gone.

One way to destroy the head of the lesion is to use over the counter wart treatments to freeze the lesions. While this is effective, it may result in permanent discoloration of the skin. Another, more localized treatment is to burn the head of the lesion. This may be accomplished by holding a pin with a pair of pliers, heating the pin over a stove till glowing, and touching the tip of the pin to the lesion. It is important to consult with a dermatologist before attempting a home remedy.

The infection can also be cleared without medicine if there are only a few lesions. First, the affected skin area should be cleaned with an alcohol swab. Next, a sterile needle is used to cut across the head of the lesion, through the central dimple. The contents of the papule are removed with another alcohol swab. This procedure is repeated for each lesion (and is therefore unreasonable for a large infection). With this method, the lesions will heal in two to three days. One purported remedy is to apply spray-on plaster daily to trigger a reduction in spots, first by becoming crusty and then disappearing.

Surgical treatment

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 burning or stinging at the treated site, which may persist for a few minutes after the treatment. Scarring or loss of color can complicate both these treatments. With liquid nitrogen, a blister may form at the treatment site, but it will slough off in two to four weeks. Although its use is banned by the FDA in the United States in its pure, undiluted form, the topical blistering agent cantharidin can be effective. It should be noted that cryosurgery and curette scraping are not painless procedures. They may also leave scars and/or permanent white (depigmented) marks.

Laser

Pulsed dye laser therapy for molluscum contagiosum may be the treatment of choice for multiple lesions in a cooperative patient (Dermatologic Surgery, 1998). The use of pulsed dye laser for the treatment of MC has been documented with excellent results. The therapy was well tolerated, without scars or pigment anomalies. The lesions resolved without scarring at 2 weeks. Studies show 96%–99% of the lesions resolved with one treatment. 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 this 585nm laser. It is important to remember that removal of the visible bumps does not cure the disease. The virus is in the skin and new bumps often appear over the course of a year until the body mounts an effective immune response to the virus. Thus any surgical treatment may require it to be repeated each time new crops of lesions appear.

Prevent spreading

To prevent molluscum contagiosum from spreading:

Try not to scratch. Put a piece of tape or a bandage over any bumps.
Avoid contact sports, and shared baths and articles of clothing (towels.)
If bumps are on the face, avoid shaving.
If bumps are on the genital area, avoid sexual activity and shaving.

Prognosis

Most cases of molluscum will clear up naturally within two years. 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, like the common cold, there is no permanent immunity to the virus, and it is possible to become infected again in the future upon exposure to an infected person.