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. The incidence of MC infections in young children is around 17% and peaks between 2-12 years of age. 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 1 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.

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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,^[1] to 2 or 3 months.^[2] However via autoinoculation, the disease may propagate and so an outbreak generally lasts longer with mean durations variously reported as 8 months,^[1] to about 18 months,^[3][4] and with a range of durations from 6 months to 5 years.^[2][4]

Treatment is often unnecessary^[5] depending on the location and number of lesions, with no single approach shown to be convincingly effective.^[6] 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.^[4] It is important to realize that treating the bumps does not cure the disease. The virus is in the skin and new bumps will often appear even after all the visible ones are surgically treated. Any surgical option of treatment may therefore have to be repeated each time new bumps occur. The body eventually mounts an effective immune response and rids itself of the virus, but until then, new bumps may occur over the course of a year or more.

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.^[7]

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).^[8] However the oil may irritate normal skin at concentrations of 1%.^[9][10]

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.^[11][12] 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.^[13] Imiquimod, 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

Non-medicine treatment

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.

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 no longer available in the United States, 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.^[14][15] 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, swimming pools, 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.

See also

• Acrochordons (also called skin tags — similar in appearance and grow in similar areas)

References