Molluscum contagiosum

What is molluscum contagiosum?

Molluscum contagiosum is a common viral skin infection. It most often affects infants and young children but adults may also be infected.

Molluscum contagiosum presents as clusters of small round bumps (papules) especially in the warm moist places such as the armpit, groin or behind the knees. They range in size from 1 to 6 mm and may be white, pink or brown. They often have a waxy, pinkish look with a small central pit (umbilicated). As they resolve, they may become inflamed, crusted or scabby. There may be few or hundreds of spots on one individual.

Molluscum contagiosum is a harmless virus but it may persist for months or occasionally for a couple of years. Molluscum contagiosum may rarely leave tiny pit-like scars.

Molluscum frequently induces dermatitis in the affected areas, which are dry, pink and itchy. An itchy rash may sometimes appear on distant sites and represents an immunological reaction or 'id' to the virus.

Molluscum contagiosum

Typical molluscum

Eczema and crusted lesions

Scarring

More images of molluscum ...

How do you catch molluscum contagiosum?

Molluscum contagiosum can be spread from person to person (especially children) by direct skin contact. This appears to be more likely in wet conditions, such as when children bathe or swim together. Sexual transmission is possible in adults.

Lesions tend to be more numerous and last longer in children who also have atopic eczema. It can be very extensive and troublesome in patients with human immunodeficiency virus infection.

Molluscum contagiosum may arise in areas that have been injured, often because they've been scratched. The papules form a row; this is known as koebnerised molluscum.

How is the diagnosis of molluscum contagiosum made?

Molluscum is usually recognised by its characteristic appearance clinically or on dermatoscopy. White molluscum bodies can often be expressed from the centre of the papules. Sometimes, diagnosis is made on seeing the histopathological features of molluscum contagiosum on skin biopsy.

Treatment

There is no single perfect treatment of molluscum contagiosum since we are currently unable to kill the virus. The soft white core can be squeezed out of individual lesions. In many cases no specific treatment is necessary.

Medical treatments include:

• Minor surgery, curettage (topical anaesthetic cream may be applied first) or laser ablation
• Cryotherapy
• Cantharidine
• Imiquimod cream
• Wart paints containing salicylic acid or podophyllin

The dermatitis may be treated with hydrocortisone cream, but is unlikely to fully resolve until the infection has cleared up.