Molluscum contagiosum

Molluscum contagiosum is an infection caused by a Poxvirus (molluscum contagiosum virus) ¹. Molluscum contagiosum is transmitted mainly by direct contact with infected skin ². The result of the infection is usually a benign, mild skin disease characterized by umbilicated pink or skin-colored papules (growths) that may appear anywhere on the body ³. Within 6-12 months, Molluscum contagiosum typically resolves without scarring but may take as long as 4 years ⁴.

Children aged 2–5 years are most commonly affected with molluscum contagiosum, although it can occur in adolescents and adults ⁵. Molluscum contagiosum is rare in children aged younger than one year ⁴. In adolescents and adults, molluscum contagiosum could occur either as a sexually transmitted disease (STD) or in relation to contact sports ⁶. Molluscum contagiosum in adults is more common in immunosuppressed patients: in the 1980s, the number of reported cases of molluscum contagiosum increased, apparently associated with the onset of the acquired immune deficiency virus (HIV) epidemic ⁷. It is estimated that in human immunodeficiency virus (HIV) patients the prevalence is close to 20% ⁸. Besides HIV, molluscum contagiosum may be associated with medically induced immunosuppression or primary immunodeficiencies (eg, DOCK8 immunodeficiency syndrome) ⁹.

Molluscum contagiosum is more prevalent in warm climates than cool ones, and in overcrowded environments ¹⁰. In the United States, it is estimated that the prevalence of molluscum contagiosum in children is less than 5% ¹¹.

Children with atopic eczema (atopic dermatitis) may be more severely affected by molluscum contagiosum due to the skin barrier breaks and immune cell dysfunction in atopic skin. In addition, these patients may be more likely to autoinoculate (excoriation of primary lesions and spread to areas of normal skin) new areas of skin because of the underlying itch (pruritus) from their atopy. However, studies on atopic dermatitis are controversial. Some studies have found an increased risk of molluscum contagiosum in patients with atopic dermatitis ¹², ¹³, with prevalence rates of atopic dermatitis in patients with molluscum contagiosum of up to 62% ¹⁴, ¹⁵. It has even been hypothesized that an increased risk of molluscum contagiosum virus infection in patients with atopic dermatitis and filaggrin mutation ¹⁶. Other studies have shown no significant differences ¹⁷.

The lesions, known as Mollusca, are small, raised, and usually white, pink, or flesh-colored with a dimple or pit in the center. They often have a pearly appearance. They’re usually smooth and firm. In most people, the lesions range from about the size of a pinhead to as large as a pencil eraser (2 to 10 millimeters in diameter). They may become itchy, sore, red, and/or swollen.

Whenever you can see the bumps on the skin, molluscum contagiosum is contagious.

Most people get about 10 to 20 bumps on their skin. If a person has a weakened immune system, many bumps often appear.

Mollusca may occur anywhere on the body including the face, neck, arms, legs, abdomen, and genital area, alone or in groups. The lesions are rarely found on the palms of the hands or the soles of the feet.

Molluscum contagiosum can be very extensive and troublesome in patients with human immunodeficiency virus (HIV) infection or that have other reasons for poor immune function.

Patients with HIV/AIDS and other immunocompromising conditions (e.g., solid organ transplant recipients) can develop “giant” lesions (≥15 mm in diameter), larger numbers of lesions (100 or more molluscum contagiosum bumps) and lesions that are more resistant to standard therapy ¹⁸, ¹⁹, ²⁰. The following diseases should be considered in the differential diagnosis of molluscum contagiosum: cryptococcosis, basal cell carcinoma, keratoacanthoma, histoplasmosis, coccidioidomycosis, and verruca vulgaris. For genital lesions, condyloma acuminata and vaginal syringomas should be considered.

Molluscum contagiosum lesions have recently come to be classified in one of three ways:

• The commonly seen skin lesions found largely on the faces, trunks, and limbs of children;
• The sexually transmitted lesions found on the abdomen, inner thighs, and genitals of sexually active adults; and
• The diffuse and recalcitrant eruptions of patients with AIDS or other immunosuppressive disorders.

Treatment of mild molluscum contagiosum infections is often not required because lesions will eventually resolve on their own. However, you can decrease the chance of spreading the infection to other parts of your body or to other people with the following guidelines:

• Do not scratch or shave the affected areas.
• Avoid sharing clothing, towels, and bedding with others.
• If the affected area is small, keep it covered.

The duration of molluscum contagiosum lesions is variable, but in most cases, they are self-limiting in a period of 6 to 9 months; however, some cases may persist for more than 3 or 4 years ²¹. It has been described a phenomenon called “beginning of the end” (BOTE) sign which refers to clinical erythema and swelling of an molluscum contagiosum skin lesion when the regression phase begins (Figure 3). This phenomenon is likely due to an immune response towards the molluscum contagiosum infection rather than a bacterial superinfection ², ¹⁵, ²².

Figure 1. Molluscum contagiosum in children

Footnote: Each molluscum contagiosum starts out as a very small spot, about the size of a pinhead, and grows over several weeks into a larger bump that might become as large as a pea or pencil eraser. A tiny dimple (indentation) often develops on the top of each molluscum contagiosum.

Figure 2. Molluscum contagiosum papules

Footnote: Firm, rounded, skin-colored papules with a shiny and umbilicated surface.

Figure 3. Molluscum contagiosum regression

Footnote: Molluscum contagiosum regression with the “beginning of the end” (BOTE) sign which refers to clinical erythema and swelling of an molluscum contagiosum skin lesion

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Molluscum contagiosum causes

Molluscum contagiosum is caused by molluscum contagiosum virus (MCV), a double-strand DNA virus which belongs to the Poxviridae family; humans are molluscum contagiosum virus only host ⁴. Molluscum contagiosum virus has 4 different genotypes: molluscum contagiosum virus 1 (MCV 1), molluscum contagiosum virus 2 (MCV 2), molluscum contagiosum virus 3 (MCV 3) and molluscum contagiosum virus 4 (MCV 4). Molluscum contagiosum virus 1 (MCV 1) is the most common genotype (75–96%), followed by molluscum contagiosum virus 2 (MCV 2), while molluscum contagiosum virus 3 (MCV 3) and molluscum contagiosum virus 4 (MCV 4) are extremely infrequent ², ²³, ²⁴. A Slovenian study ²³ showed that in children molluscum contagiosum virus 1 (MCV 1) infection is more frequent than in adults, and in adult women, molluscum contagiosum virus 2 (MCV 2) infection is more frequent than molluscum contagiosum virus 1 (MCV 1).

Molluscum contagiosum virus infects the epidermis and replicates in the cytoplasm of cells with a variable incubation period between two and six weeks ¹⁴. Different studies have been developed to sequence the genome of molluscum contagiosum virus (MCV) and determine possible genes involved in the evasion of the host immune response, a hypothesis that arose based on the absence of inflammation observed in histopathological samples of infected skin ²⁵, ²⁶. To date, four viral genes have been identified that code proteins that would alter the activation of the nuclear factor kB (NF-kB): MC159, MC160, MC132, and MC005 ²⁶, ²⁷, ²⁸, ²⁹. Nuclear factor kB (NF-kB) is a nuclear protein complex present in dendritic cells that regulate the transcription of DNA and facilitate the synthesis of pro-inflammatory cytokines (TNF, IL-1, IL-6, among others) and activation of innate and acquired immune response ³⁰. Brady et al ²⁶ have seen that MC132 and MC005 proteins would alter the activation of NF-kB by inhibiting pattern recognition receptors (PRRs). Added to this, MC132 would bind and stimulate the degradation of the p65 subunit of NF-kB and MC005 would inhibit the activation of the IKK complex (IkB kinase) binding to active NEMO subunit (essential modulator of NF-kB).

Molluscum contagiosum virus is transmitted by direct contact with infected skin, which can be sexual, non-sexual, or by autoinoculation ⁴. Additionally, it can be transmitted by contaminated fomites like bath sponges or towels ². It has been associated with the use of the swimming pool ¹⁴.

There are several ways the molluscum contagiosum virus can spread ³¹:

• 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 molluscum contagiosum 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.

How do people get molluscum contagiosum?

The virus that causes molluscum spreads from direct person-to-person physical contact and through contaminated fomites. Fomites are inanimate objects that can become contaminated with virus; in the instance of molluscum contagiosum this can include linens such as clothing and towels, bathing sponges, pool equipment, and toys. Although the virus might be spread by sharing swimming pools, baths, saunas, or other wet and warm environments, this has not been proven. Researchers who have investigated this idea think it is more likely the virus is spread by sharing towels and other items around a pool or sauna than through water.

Someone with molluscum contagiosum can spread it to other parts of their body by touching or scratching a lesion and then touching their body somewhere else. This is called autoinoculation. Shaving and electrolysis can also spread mollusca to other parts of the body.

Molluscum contagiosum can spread from one person to another by sexual contact ¹. Many, but not all, cases of molluscum in adults are caused by sexual contact ¹.

Conflicting reports make it unclear whether the disease may be spread by simple contact with seemingly intact lesions or if the breaking of a lesion and the subsequent transferring of core material is necessary to spread the virus.

Molluscum contagiosum lesions can also be congenital when transmitted vertically from mother to baby by contact with molluscum contagiosum virus in the birth canal ³², ³³. In this case, molluscum contagiosum lesions are typically located on the scalp and have a circular arrangement ³³. Other sites of atypical location, in addition to the oral mucosa ², include the palms and soles, the areola/nipple ³⁴, ³⁵, the conjunctiva ³⁶, lips ³⁷, eyelids ³⁸, among others ³⁹. Clinical presentation of periocular lesions has been described as erythematous, nodular umbilicated, big/giant, conglomerated, inflamed, or pedunculated ⁴⁰. The periocular presentation has also been associated with conjunctivitis ⁴¹.

The molluscum contagiosum virus remains in the top layer of skin (epidermis) and does not circulate throughout the body; therefore, it cannot spread through coughing or sneezing ¹.

Since the virus lives only in the top layer of skin, once the lesions are gone the virus is gone and you cannot spread it to others ¹. Molluscum contagiosum is not like herpes viruses, which can remain dormant (“sleeping”) in your body for long periods and then reappear.

Who is at risk for molluscum contagiosum infection?

Molluscum contagiosum is common enough that you should not be surprised if you see someone with it or if someone in your family becomes infected. Although not limited to children, it is most common in children 1 to 10 years of age.

People at increased risk for getting the disease include:

• People with weakened immune systems (i.e., HIV-infected persons or persons being treated for cancer) are at higher risk for getting molluscum contagiosum. Their growths may look different, be larger, and be more difficult to treat.
• Atopic dermatitis may also be a risk factor for getting molluscum contagiosum due to frequent breaks in the skin. People with this condition also may be more likely to spread molluscum contagiousm to other parts of their body for the same reason.
• People who live in warm, humid climates where living conditions are crowded.

In addition, there is evidence that molluscum contagiosum infections have been on the rise in the United States since 1966, but these infections are not routinely monitored because they are seldom serious and routinely disappear without treatment.

How can you prevent molluscum contagiosum from spreading?

The best way to avoid getting molluscum contagiosum is by following good hygiene habits. Remember that the virus lives only in the skin and once the lesions are gone, the virus is gone and you cannot spread the virus to others.

Wash your hands

There are ways to prevent the spread of molluscum contagiosum. The best way is to follow good hygiene (cleanliness) habits. Keeping your hands clean is the best way to avoid molluscum infection, as well as many other infections. Hand washing removes germs that may have been picked up from other people or from surfaces that have germs on them.

Don’t scratch or pick at molluscum contagiosum lesions

It is important not to touch, pick, or scratch skin that has lesions, that includes not only your own skin but anyone else’s. Picking and scratching can spread the virus to other parts of the body and makes it easier to spread the disease to other people too.

Keep molluscum contagiosum lesions covered

It is important to keep the area with molluscum lesions clean and covered with clothing or a bandage so that others do not touch the lesions and become infected. Do remember to keep the affected skin clean and dry.

Any time there is no risk of others coming into contact with your skin, such as at night when you sleep, uncover the lesions to help keep your skin healthy.

Be careful during sports activities

Do not share towels, clothing, or other personal items.

People with molluscum contagiosum should not take part in contact sports like wrestling, basketball, and football unless all lesions can be covered by clothing or bandages.

Activities that use shared gear like helmets, baseball gloves and balls should also be avoided unless all lesions can be covered.

Swimming should also be avoided unless all lesions can be covered by watertight bandages. Personal items such as towels, goggles, and swim suits should not be shared. Other items and equipment such as kick boards and water toys should be used only when all lesions are covered by clothing or watertight bandages.

Swimming pools

Parents and others often ask if molluscum virus can spread in swimming pools. There is also concern that it can spread by sharing swimming equipment, pool toys, or towels.

Some investigations report that spread of molluscum contagiosum is increased in swimming pools. However, it has not been proved how or under what circumstances swimming pools might increase spread of the virus. Activities related to swimming might be the cause. For example, the virus might spread from one person to another if they share a towel or toys. More research is needed to understand if and for how long the molluscum virus can live in swimming pool water and if such water can infect swimmers.

Open sores and breaks in the skin can become infected by many different germs. Therefore, people with open sores or breaks from any cause should not go into swimming pools.

If a person with molluscum contagiosum is going swimming, they should:

• Cover all visible lesions with watertight bandages
• Dispose of all used bandages at home
• Not share towels, kick boards, other equipment, or toys.

Day care centers and schools

There is no reason to keep a child with molluscum infection home from day care or school.

If you notice bumps on a child’s skin, it is reasonable to inform the child’s parents and to request a doctor’s note. Only a healthcare professional can diagnose molluscum contagiosum because there are many other causes of growths on the skin, both infectious and non-infectious.

Lesions not covered by clothing should be covered with a watertight bandage. Change the bandage daily or when obviously soiled.

If a child with lesions in the underwear/diaper area needs assistance going to the bathroom or needs diaper changes, then lesions in this area should be bandaged too if possible.

Covering the lesions will protect other children and adults from getting molluscum contagiosum and will also keep the child from touching and scratching the lesions, which could spread the infection to other parts of his/her body or cause secondary (bacterial) infections.

Children should be reminded to wash their hands frequently.

If day care or school employees with regular physical contact with others are normally required to have skin examinations during pre-employment physicals, then infection molluscum contagiosum should be noted.

Work

Although there has been only one reported case of healthcare provider-to-patient transmission of molluscum contagiosum, if an employee who comes in physical contact with clients regularly, such as an aesthetician or health care provider, is diagnosed with molluscum contagiosum by a health care professional, it would be reasonable to require that he/she cover visible lesions with a watertight dressing while at work. Otherwise, no special precautions are needed.

Other precautions can prevent or reduce spread to uninfected people:

• Frequent and correct hand hygiene practices.
• Requiring notation of molluscum contagiosum on examinations requested for—
  • Employment
    • Recommended only for employees with regular physical contact with clients (e.g., aestheticians, health care professionals, day care employees) who are normally required to have skin examinations during pre-employment physicals.
  • Camp
  • Sports physicals
• Recommending that all visible lesions be covered by a watertight dressing, if molluscum contagiosum is diagnosed by a healthcare professional during a physical examination.
• Routinely disinfecting shared equipment (e.g., kick boards, wrestling mats). The molluscum contagiosum virus is not particularly difficult to kill and usual sanitation procedures should be sufficient.

Other ways to avoid sharing your molluscum contagiosum infection

Do not shave or have electrolysis on areas with lesions.

Don’t share personal items such as unwashed clothes, hair brushes, wrist watches, and bar soap with others.

If you have lesions on or near the penis, vulva, vagina, or anus, avoid sexual activities until you see a health care provider.

Molluscum contagiosum signs and symptoms

Molluscum contagiosum presents as clusters of small round dome-shaped papules (bumps). The firm rounded papules range in size from 2 to 10 mm and may be white, skin-colored, pink, pearly or brown and occur in clusters and sometimes in a straight line. 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. The molluscum contagiosum papules (bumps) may be single, multiple or clustered, and occasionally they may have an erythematous halo or be pediculated. Pruritus (itch) may be present.

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.

The bumps are usually painless and may occasionally itch. When molluscum contagiosum is autoinoculated by scratching, the papules often form a row. Individual bumps may get bigger over the course of 6–12 weeks. Usually the bumps do not grow larger than 10 mm, but in patients with weak immune systems, they can be larger than a nickel.

Molluscum contagiosum frequently induces dermatitis around them and affected skin becomes pink, dry and itchy. As the papules resolve, they may become inflamed, crusted or scabby for a week or two.

Molluscum contagiosum infections may be:

• Mild – under 10 lesions
• Moderate – about 10–50 lesions
• Severe – over 50 lesions

Common areas for molluscum contagiosum lesions are the chest, abdomen, back, armpits, groin, or backs of the knees. Occasionally, they can be seen on the face and genital region. Because the incubation period for molluscum contagiosum is 2 weeks to 6 months, lesions may not immediately be seen after contracting the virus. Molluscum contagiosum infection is self-limited, and lesions will go away on their own in 6–9 months, although they rarely can persist for a few years. As the bumps begin to resolve, they may initially appear more inflamed, with pus and crusting of the lesions, before they eventually fade. They usually do not leave a scar.

In children, the main affected areas are sites of exposed skin, such as the trunk, extremities, intertriginous regions, genitals, and face, except the palms and soles ⁴². The involvement of the oral mucosa is rare ⁴³. In adults, lesions are most frequently located in the lower abdomen, thighs, genitals, and perianal area, most of the cases transmitted by sexual contact ⁴. In children, genital lesions are mainly due to autoinoculation and are not pathognomonic of sexual abuse ⁴⁴.

Molluscum contagiosum complications

Complications of Molluscum contagiosum can include:

• Secondary bacterial infection from scratching (impetigo)
• Conjunctivitis when the eyelid is infected
• Disseminated secondary eczema; this represents an immunological reaction or ‘id’ to the virus
• Numerous and widespread molluscum contagiosum that are larger than usual may occur in immune-deficient patients (such as uncontrolled HIV infection or in patients on immune
• suppressing drugs), and often affect the face
• Spontaneous, pitted scarring
• Scarring due to surgical treatment

Molluscum contagiosum diagnosis

Your doctor will most likely be able to diagnose molluscum contagiosum by its appearance. Molluscum is usually recognized by its characteristic clinical appearance or on dermatoscopy (Figure 4) ². White molluscum bodies can often be expressed from the center of the papules.

Very rarely, a biopsy is required. Histopathology shows characteristic intracytoplasmic eosinophil inclusion bodies known as Henderson-Petterson bodies (Figure 5).

Figure 4. Molluscum contagiosum dermatoscopic findings

Footnote: Polarized-light dermoscopy, original magnification 10×. Dermatoscopic findings of molluscum contagiosum. (Red arrows) white-to-yellow polylobular structures. (Blue arrows) crown vessels.

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Figure 5. Molluscum contagiosum histopathology

Footnote: Molluscum contagiosum histopathology showing large intracytoplasmic eosinophil inclusion bodies called Henderson-Petterson bodies.

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Molluscum contagiosum differential diagnosis

Molluscum contagiosum differential diagnoses include mainly inflammatory, infectious, and neoplastic etiologies; they mainly differ according to the age and immunologic status of the patient ². In immunosuppressed patients, the main differential diagnosis includes histoplasmosis and cryptococcosis which can be seen as umbilicated papules ⁴⁵.

Molluscum contagiosum differential diagnosis ², ⁴⁶, ⁴⁷, ⁴⁸, ⁴⁹, ⁵⁰, ¹⁵, ⁵¹:

• Infections
  • Verruca vulgaris
  • Chickenpox
  • Folliculitis
  • Condyloma acuminatum
• Tumors
  • Syringomas
  • Steatocystoma multiplex
  • Basal cell carcinoma
• Miscellaneous
  • Acne vulgaris
  • Gianotti-Crosti syndrome
  • Milia
  • Sebaceous hyperplasia
• Papular urticaria

Molluscum contagiosum treatment

Molluscum contagiosum viral skin infection will resolve on its own within a few months. Talk to your child’s doctor about whether he or she recommends treatment or watchful waiting. No treatment is 100% effective since scientists are currently unable to kill the virus, and most can have side effects such as pain or irritation of the skin.

There is a consensus among experts that molluscum contagiosum treatment should be indicated in patients with extensive disease, secondary complications (bacterial superinfection, molluscum dermatitis, conjunctivitis), or aesthetic complaints ².

Treatment for molluscum is usually recommended if lesions are in the genital area (on or near the penis, vulva, vagina, or anus) ⁵². If lesions are found in this area it is a good idea to visit your healthcare provider as there is a possibility that you may have another disease spread by sexual contact.

A retrospective study ⁵³ evaluated the resolution rate of molluscum contagiosum lesions in treated and untreated patients, showing a resolution at 12 months of 45.6% in the treated group and 48.8% in the untreated group. At 18 months, they found a resolution rate of 69.5% and 72.6% in the treated versus the untreated group, respectively. From this cardinal study ⁵³, it appears that active treatment does not improve the resolution rate when compared to observation alone.

• Be aware that some treatments available through the internet may not be effective and may even be harmful.

What are the treatment options for molluscum contagiosum?

Because molluscum contagiosum is self-limited in healthy individuals, treatment may be unnecessary. Nonetheless, issues such as lesion visibility, underlying atopic disease, and the desire to prevent transmission may prompt therapy.

Active treatments can be classified as phyiscal removal, chemical, immunomodulatory, and antiviral ².

Possible treatments include the following:

• Cantharidin 0.7% or 0.9% liquid – This is an extract from the blister beetle. It is applied to the lesions and then washed off in 2–6 hours. It is not for use on the face or genitals.
• Removal with freezing (cryosurgery), scraping (curettage), or burning (electrocautery) – All of these options may be painful.
• Salicylic acid
• Podofilox (Condylox®)
• Tretinoin (Retin-A®)
• Trichloroacetic acid
• Silver nitrate paste
• Imiquimod cream (Aldara®) – This may be useful for widespread, difficult-to-treat lesions.

Physical removal

Physical removal of lesions may include cryotherapy (freezing the lesion with liquid nitrogen), curettage (the piercing of the core and scraping of caseous or cheesy material), and laser therapy. These options are rapid and require a trained health care provider, may require local anesthesia, and can result in post-procedural pain, irritation, and scarring.

• It is not a good idea to try and remove lesions or the fluid inside of lesions yourself. By removing lesions or lesion fluid by yourself you may unintentionally autoinoculate other parts of your body or risk spreading it to others. By scratching or scraping your skin you could cause a bacterial infection.

Cryotherapy is an effective treatment. It can be applied with a cotton-tipped swab or by portable sprayers, 1 or 2 cycles of 10 to 20 seconds are typically used ³. A prospective, randomized and comparative trial ⁵⁴ evaluated the efficacy of cryotherapy in molluscum contagiosum treatment. The study demonstrated a complete clearance in 70.7% of the patients at 3 weeks and in 100% of them at 16 weeks ⁵⁴. Another study ⁵⁵ showed full clearance in 83.3% of 60 patients (average age of 20 years) at 6 weeks. In both, the application of cryotherapy was administered weekly. The disadvantages of cryotherapy are the possibility of blistering, scarring, and post-inflammatory hypo or hyperpigmentation ³.

Curettage is also an effective method and involves the physical removal of skin lesions ³. One study showed that of 1,879 children, 70% were cured with one session while 26% needed two sessions, with overall satisfaction of 97% in both parents and children ⁵⁶. A randomized, controlled trial ⁵⁷ showed a complete clearance with only one curettage session in 80.3% of the patients and without recurrences at 6 months of follow-up. It can be done with a curette, punch biopsy or with an ear speculum ⁵⁸, ⁵⁹. To reduce pain, topical application of EMLA (eutectic mixture of local anesthetics), a combination of 2.5% lidocaine and 2.5% prilocaine, may be required 1 hour before the procedure ⁵⁶, ⁶⁰. Curettage can cause pain, bleeding, and scarring.

After curettage, topical povidone iodine can be applied. This is an antiseptic useful in the treatment of molluscum contagiosum based on case reports ⁶¹. A Cochrane systematic review of 2017 showed that povidone-iodine 10% potentiates the effect of 50% salicylic acid, without adverse effects reported ²¹. For topical povidone iodine, an application scheme of 3 times a day until the resolution of the cutaneous lesions.

Another useful mechanical method is pulse dye laser therapy, which due to its costs and limited availability is suggested to be left for refractory cases ⁶², ². It is an effective, safe, and well-tolerated treatment, with infrequent adverse effects ⁶². Cases of successful use in immunosuppressed patients have also been reported ⁶³.

Oral therapy

Gradual removal of lesions may be achieved by oral therapy. This technique is often desirable for children because it is generally less painful and may be performed by parents at home in a less threatening environment. Oral cimetidine has been used as an alternative treatment for small children who are either afraid of the pain associated with cryotherapy, curettage, and laser therapy or because the possibility of scarring is to be avoided. Oral cimetidine is an H2 (histamine-2) receptor antagonist that would stimulate the delayed hypersensitivity response ³.

While cimetidine is safe, painless, and well tolerated and the recommended dose is 25–40 mg/kg/day, facial molluscum contagiosum do not respond as well as lesions elsewhere on the body ².

Topical therapy

Topical therapy destroy skin lesions through the inflammatory response they produce. Podophyllotoxin cream (0.5%) is reliable as a home therapy for men but is not recommended for pregnant women because of presumed toxicity to the fetus. Each lesion must be treated individually as the therapeutic effect is localized. Other options for topical therapy include iodine and trichloroacetic acid, salicylic acid, lactic acid, glycolic acid, benzoyl peroxide, potassium hydroxide (KOH), tretinoin, cantharidin (a blistering agent usually applied in an office setting), and imiquimod (T cell modifier) ², ³, ⁶¹. These treatments must be prescribed by a health care professional.

Cantharidin is a topical agent, an inhibitor of phosphodiesterase, which produces an intraepidermal blister, followed by resolution of the lesion and healing without a scar in some cases ⁶⁴. The efficacy of cantharidin in the treatment of molluscum contagiosum is variable, with cure rates varying between 15.4% and 100% among the different studies ⁶⁵, ⁶⁶. It is recommended to apply cantharidin 0.7–0.9% at the site of the lesion, with or without occlusion, and to wash with soap and water 2–4 hours later, each every 2–4 weeks until the resolution of lesions ³, ⁵⁷, ⁶⁴. In the face and anogenital region it should be used with precaution due to the risk of bacterial superinfection of blisters that form after 24–48 hours ³, ⁶⁷.

Potassium hydroxide (KOH) is an alkaline compound that dissolves keratin ³. Potassium hydroxide (KOH) has been used in concentrations and therapeutic schemes that vary from 5% to 20%, two times a day or every other day for 1 week or until inflammation develops ⁶⁸. A recent study ⁶⁹ showed that 10% and 15% potassium hydroxide clear lesions of molluscum contagiosum entirely in 58.8% and 64.3% of the patients, respectively. It would be a safe and effective treatment that could be applied by patients, and its effectiveness has been compared with cryotherapy and imiquimod without significant differences ⁶⁸, ⁷⁰.

Immunomodulatory methods

Immunomodulatory methods stimulate the patient’s immune response against the infection. Imiquimod is an immune-stimulatory agent agonist of the toll-like receptor 7 that activates the innate and acquired immune response ³. Imiquimod is a useful alternative in the treatment of molluscum contagiosum based on case reports and uncontrolled studies ²², ⁷¹. However, imiquimod has not been proven effective for the treatment of molluscum contagiosum in children and is not recommended for children due to possible adverse events ⁷².

A prospective, randomized trial ⁵⁴ compared the efficacy of cryotherapy with 5% imiquimod, demonstrating a complete clearance in 100% of the patients at 16 weeks for cryotherapy versus 92% for imiquimod 5% (difference not statistically significant). Cutaneous adverse effects were more frequent in the cryotherapy group. However, a recent Cochrane systematic review showed that it is not better than placebo in short-term improvement (3 months) or long-term cure (more than 6 months) and may produce adverse effects at the application site such as pain, blistering, scars and/or pigmentary changes ²¹. The current evidence positions imiquimod as a controversial therapeutic alternative ⁷³.

Other immunomodulatory methods are oral cimetidine, interferon alfa, candidin, and diphencyprone.

Candidin is intralesional immunotherapy derived from the purified extract of Candida albicans. It is an alternative in the treatment of molluscum contagiosum, being applied purely or diluted at 50% with lidocaine in a dose of 0.2–0.3 mL intralesional every 3 weeks ³. A retrospective study evaluating the efficacy of candidin in the treatment of molluscum contagiosum showed a complete resolution rate of 55% and a partial resolution of 37.9%, with an overall response rate of 93% ⁷⁴.

Diphencyprone is a topical immunomodulator used in multiple skin diseases. Cases of successful treatment with diphencyprone have been reported in immunosuppressed and immunocompetent patients ⁷⁵, ⁷⁶.

Therapy for immunocompromised persons

Most therapies are effective in immunocompetent patients; however, patients with HIV and AIDS or other immunosuppressing conditions often do not respond to traditional treatments. In addition, these treatments are largely ineffective in achieving long-term control in HIV patients.

Low CD4 cell counts have been linked to widespread facial mollusca and therefore have become a marker for severe HIV disease. Thus far, therapies targeted at boosting the immune system have proven the most effective therapy for molluscum contagiosum in immunocompromised persons. In extreme cases, intralesional interferon alfa has been used to treat facial lesions in these patients. Interferon alfa is a proinflammatory cytokine that is used in the treatment of molluscum contagiosum in immunosuppressed patients with severe or refractory disease. It can be administered subcutaneously or intralesionally ⁷⁷, ⁷⁸, ⁷⁹. However, the severe and unpleasant side effects of interferon, such as influenza-like symptoms, site tenderness, depression, and lethargy, make it a less-than-desirable treatment. Furthermore, interferon therapy proved most effective in otherwise healthy persons.

Another method used in immunosuppressed patients with extensive or refractory disease is cidofovir, an antiviral drug initially used in cytomegalovirus retinitis in HIV patients. It can be used topically at a concentration of 1–3% or intravenously ⁸⁰, ⁸¹, ⁸². The major problem with intravenous administration is nephrotoxicity ⁸³.

Radiation therapy is also of little benefit.

New therapies

New molluscum contagiosum treatments include topical sinecatechins ⁸⁴, intralesional 5-fluorouracil (5 FU) ⁸⁵, hyperthermia ⁸⁶ and zoster immune globulin (ZIG) ⁸⁷. Evidence is preliminary to determine the effectiveness of these therapies.

What are the long-term effects of molluscum contagiosum?

In immune competent hosts, molluscum contagiosum is a relatively harmless. 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. Contact with another infected individual later on can lead to a new crop of mollusca.

Infection can be very persistent in the presence of significant immune deficiency.

Molluscum contagiosum doesn’t usually cause any long-term problems. The growths typically don’t leave any marks. Treatments might scar the skin, though, and some people develop an infection that needs to be treated with antibiotics.

Recovery from one molluscum infection does not prevent future infections. Molluscum contagiosum is not like herpes viruses which can remain dormant (“sleeping”) in your body for long periods of time and then reappear. If you get new molluscum contagiosum lesions after you are cured, it means you have come in contact with an infected person or object again.

Complications of molluscum contagiosum

The lesions caused by molluscum contagiosum are usually benign and resolve without scarring. However scratching at the lesion, or using scraping and scooping to remove the lesion, can cause scarring. For this reason, physically removing the lesion is not often recommended in otherwise healthy individuals.

The most common complication is a secondary infection caused by bacteria. Secondary infections may be a significant problem in immunocompromised patients, such as those with HIV/AIDS or those taking immunosuppressing drug therapies. In these cases, treatment to prevent further spread of the infection is recommended.

Molluscum contagiosum prognosis

In immunecompetent hosts, molluscum contagiosum is relatively harmless with lesions resolving without scarring. 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. Contact with another infected individual later on can lead to a new crop. However scratching at the lesion, or using scraping and scooping to remove the lesion, can cause scarring. For this reason, physically removing molluscum contagiosum is not often recommended in otherwise healthy individuals.

Infection can be very persistent in the presence of significant immune deficiency. The most common complication is a secondary infection caused by bacteria. Secondary infections may be a significant problem in immunocompromised patients, such as those with HIV/AIDS or those taking immunosuppressing drug therapies. In these cases, treatment to prevent further spread of the infection is recommended. In people living with HIV/AIDS, molluscum contagiosum is best managed with highly active antiretroviral therapy (HAART) ⁸⁸.

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