What is molluscum contagiosum?
Molluscum contagiosum is a common viral skin infection of infants and young children. Adolescents and adults are less often infected.
How does molluscum contagiosum present?
Molluscum contagiosum presents as clusters of small round papules (bumps). They mostly arise in warm moist places, such as the armpit, groin or behind the knees. The papules 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 (this appearance is sometimes described as umbilicated). There may be few or hundreds of spots on one individual.
Molluscum frequently induces dermatitis in the affected areas, which become dry, pink and itchy. As the papules resolve, they may become inflamed, crusted or scabby for a week or two. An itchy rash may sometimes appear on distant sites and represents an immunological reaction or 'id' to the virus.
Eczema and crusted lesions
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.
Molluscum papules 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 (HIV) infection. In adults with high-risk sexual behaviour, molluscum contagiosum located in genital areas can be the first symptom of HIV 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.
What is the treatment for molluscum contagiosum?
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, which may trigger them to clear. In many cases no specific treatment is necessary.
Medical treatments include:
- Antiseptics such as 1% hydrogen peroxide cream under occlusion or 10% povidone iodine solution
- Cantharidine solution
- Wart paints containing salicylic acid or podophyllin
- Minor surgery, curettage (topical anaesthetic cream may be applied first) or laser ablation
The secondary dermatitis may be treated with a mild topical corticosteroid such as hydrocortisone cream, but is unlikely to fully resolve until the molluscum infection has cleared up.
Although sometimes prescribed for molluscum contagiosum, clinical trials have not shown imiquimod cream to be of benefit.
How long does molluscum contagiosum persist?
Molluscum contagiosum is a harmless virus. The papules may persist for up to 2 years or longer. In children, about half of cases have cleared by 12 months, and two-thirds by 18 months, with or without treatment.
Tiny pit-like scars may be left behind after the molluscum contagiosum clears up.
- Semkova K, Palamaras I, Robles W. Hydrogen peroxide 1% cream under occlusion for treatment of molluscum contagiosum in an 8-month-old infant: an effective and safe treatment option. Clin Exp Dermatol. 2014 Jun;39(4):560-1. doi: 10.1111/ced.12344. PubMed PMID: 24825145.
- H Basdag, BM Rainer, BA Cohen. Molluscum Contagiosum: To Treat or Not to Treat? Experience With 170 Children in an Outpatient Clinic Setting in the Northeastern United States. Pediatr Dermatol 2015 Jan 30;[EPub Ahead of Print]
On DermNet NZ:
- Molluscum Contagiosum – Medscape Reference
- Dermatologic Manifestations of Molluscum Contagiosum – Medscape Reference
- Pediatric Molluscum Contagiosum – Medscape Reference
- Molluscum Contagiosum in Emergency Medicine – Medscape Reference
- Ophthalmologic Manifestations of Molluscum Contagiosum – Medscape Reference
- Poxviruses – Medscape Reference
- Molluscum Contagiosum – EmedicineHealth
- Molluscum Contagiosum – British Association of Dermatologists
- Molluscum (Molluscum Contagiosum) – CDDC
- Patient information: Molluscum contagiosum (Beyond the Basics) – UpToDate (for subscribers)
- Problematic Use of Imiquimod for Molluscum Contagiosum in Children Practice Update review
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