Molluscum contagiosum is a common viral skin infection of childhood that causes localised clusters of epidermal papules called mollusca and mainly affects infants and young children under the age of 10 years. It is more prevalent in warm climates than cool ones, and in overcrowded environments. Adolescents and adults are less often infected.
What causes molluscum contagiosum?
It is caused by a poxvirus, the molluscum contagiosum virus. There are at least 4 viral subtypes.
There are several ways it can spread.
- Direct skin-to-skin contact
- Indirect contact via shared towels or other items
- Auto-inoculation into another site by scratching or shaving
- Sexual transmission in adults
Transmission of mollusca appears to be more likely in wet conditions, such as when children bathe or swim together. The incubation period is usually about 2 weeks but can be as long as 6 months.
What are the clinical features of molluscum contagiosum?
Molluscum contagiosum presents as clusters of small round papules. The papules range in size from 1 to 6 mm, and may be white, pink or brown. They often have a waxy, shiny look with a small central pit (this appearance is sometimes described as umbilicated). Each papule contains white cheesy material.
There may be few or hundreds of papules on one individual. They mostly arise in warm moist places, such as the armpit, behind the knees, groin or genital areas. They can arise on the lips or rarely inside the mouth. They do not occur on palms or soles.
When mollusca are autoinoculated by scratching, the papules often form a row.
Mollusca frequently induce dermatitis around them, which becomes pink, dry and itchy. As the papules resolve, they may become inflamed, crusted or scabby for a week or two.
What is the treatment for molluscum contagiosum?
Physical treatments include:
- Picking out the soft white core (note, this could lead to autoinoculation)
- Cryotherapy (can leave white marks)
- Gentle curettage or electrodessication (can scar)
- Laser ablation (can scar)
Medical treatments include:
- Antiseptics such as hydrogen peroxide cream or povidone iodine solution
- Podophyllotoxin cream
- Wart paints containing salicylic acid
- Cantharidine solution
How can molluscum contagiosum be prevented?
To reduce spread:
- Keep hands clean
- Avoid scratching or shaving
- Cover all visible lesions with clothing or watertight bandages
- Dispose of used bandages
- Do not share towels, clothing or other personal effects
- Adults should practice safe sex or abstinence