Molluscum contagiosum is a common viral skin infection that causes benign lesions or “bumps” on the skin. The lesions are white, pink or flesh colored, and have a dip in the center. They are pearly in appearance, firm to the touch and range in size from two millimeters (i.e., pinhead) to five millimeters (i.e., pencil eraser) in diameter. Molluscum contagiosum is a contagious disease and can spread through direct contact with the skin of an infected person, or a contaminated surface.
Molluscum contagiosum is mostly observed in children, but can affect adults, in particular those with a compromised immune system. The lesions form anywhere on the body, but are uncommon on the palms of the hands or the soles of the feet. While the average person may see 10-20 lesions, the number increases significantly (more than 100) in those with compromised immunity, for example HIV/AIDS patients.
In otherwise healthy individuals, the disease clears up within 6-12 months. Topical treatment or surgical removal of the lesions may be recommended in order to prevent spread of the virus. Picking or surgical removal of the lesions may leave scars. Open lesions also carry the risk of secondary infection by bacteria.
Causes and Risk Factors
Molluscum contagiosum is caused by a poxvirus, the family of large DNA viruses that include smallpox and monkeypox. This virus lives in the skin lesions and can spread in two ways:
Skin-to-skin contact: Direct contact with lesions allows the virus to transmit to a new individual. Sexual contact is the primary route of transmission in teens and adults. Children often pick up the virus through contact with other children in a childcare setting. Scratching and breaking the lesions increases transmission and can spread the virus to skin on other parts of the body (self-re-infection). It is not yet clear whether intact lesions can transmit virus.
Contact with an infected surface: Direct contact with infected clothing, toys, bed linens, towels, mats and other personal items can transmit the molluscum contagiosum virus. Sharing of contaminated towels is the likely reason why swimming sports have a high risk of disease transmission.
Risk factors for molluscum contagiosum include the following:
Age: Molluscum contagiosum is most common in children between 1-10 years of age.
Poor immunity: AIDS, cancer therapy, and other circumstances that weaken the immune system increase the likelihood of an infection. In fact, a severe form of molluscum contagiosum, which is recognized by an increase in size and frequency of lesions, is often the sign of an undiagnosed HIV infection.
Atopic dermatitis: Eczema causes breaks in the skin, making it more prone to infection as well as self-re-infection.
Climate: The molluscum contagiosum virus easily spreads in crowded environments with a warm, humid climate.
Geography: The incidence of molluscum contagiosum is higher in developing countries.
Painless bumps on the skin’s surface are the main symptom associated with molluscum contagiosum. In children, they are found in all areas of the body, including the face, neck, armpits, arms and tops of the hands. In adults, the virus is commonly transmitted via sexual contact and is often found on the genitals, thighs and lower abdomen. The bumps appear roughly seven weeks following exposure to the virus and display the following features:
Small, firm bumps that are between 2-5 millimeters in diameter
White, pink or flesh colored with a waxy (pearly) appearance
Indentation or dimple in the center, filled with a waxy substance
Can spread to unaffected skin if scratched or picked off
Become red or inflamed as the immune system fights the virus
Are large in size (more than15 millimeters in diameter) and number (more than 100) when the host immune system is compromised (e.g., patients with HIV/AIDS).
Diagnosis and Treatment
Molluscum contagiosum is diagnosed by visual inspection of the lesions. If necessary, a scraping from the lesion is analyzed by microscopy to verify the diagnosis.
The molluscum contagiosum lesions usually clear on their own over the course of 6-12 months, at which point the patient is no longer contagious. Intervention is rarely used in pediatric patients due to the risk of adverse reactions. However, in adults and those with compromised immune systems, the lesions are often treated in order to prevent further spread. The treatment options depend on the patient’s overall health and the frequency and location of lesions.
Topical treatment: Topical creams and ointments are applied to each lesion, often repeatedly for several weeks until all lesions are treated. Imiquimod treats the lesion by triggering a local immune response. Topical creams containing retinoids, or solutions with skin irritants (e.g., salicylic acid or potassium hydroxide) are also used to destroy the lesions.
Surgery: Surgical methods remove the lesions by freezing with liquid nitrogen (cryosurgery), physical scraping (curettage) or laser (laser surgery). These procedures are performed under local anesthesia and can leave scars.
Oral treatments: Oral cimetidine is used as a systemic treatment in some pediatric patients. Unlike the topical creams and surgery, this approach is pain-free and does not cause scarring.
Combination therapy: Immunocompromised patients do not respond well to routine treatments for molluscum contagiosum and require a combination of approaches. Treatments aimed at boosting the immune system have been most effective. Laser removal and some topical treatments are also used.
Infection with molluscum contagiosum does not provide immunity to future re-infection. The following are effective ways to prevent transmission of molluscum contagiosum.
Wash your hands
Cover the lesions
Avoid scratching or picking of the lesions
Avoid swimming unless the lesions are covered with water-tight bandages
Avoid contact sports unless all lesions are covered
Avoid shaving, combing and other activities that irritate the lesions
Do not share personal items including toiletries, clothes, linens and towels.
“Molluscum contagiosum”. Mayo Clinic. Retrieved Jan. 6, 2016. http://www.mayoclinic.org/diseases-conditions/molluscum-contagiosum/basics/definition/con-20026391.
“Molluscum contagiosum”. Centers for Disease Control and Prevention (CDC). Retrieved Jan. 6, 2016. http://www.cdc.gov/poxvirus/molluscum-contagiosum/index.html.
“Molluscum contagiosum”. American Academy of Dermatology (AAD). Retrieved Jan. 6, 2016. https://www.aad.org/public/diseases/contagious-skin-diseases/molluscum-contagiosum.
Tina is a Life Science Writer for a number of online publications, including Innerbody.com. Her expertise is in conveying complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. In her spare time, she enjoys drawing science-related cartoons.