Molluscum Contagiosum

What is Molluscum Contagiosum

Molluscum contagiosum is a skin infection that can cause a rash.

Your rash may go away on its own, or you may need to have a procedure or use medicine to treat the rash.

7 Interesting Facts of Molluscum Contagiosum

  1. Molluscum contagiosum is a self-limited eruption of benign skin lesions with a characteristic appearance caused by cutaneous poxvirus infection. The groups most commonly affected are young children, sexually active young adults, and patients with HIV and very low CD4 counts
  2. Transmitted by skin-to-skin contact
  3. In children, trunk and proximal extremities are commonly affected, although lesions can occur on any part of the body, including face and genitals, via autoinoculation. Sexually transmitted infection in adults primarily affects the perineum and thighs
  4. Diagnosis is clinical, by visual recognition of the characteristic skin-colored, dome-shaped, smooth, pearly papules with central umbilication; if diagnosis is uncertain, histopathology is diagnostic
  5. Because disease is self-limited, treatment is not required in children unless cosmesis, autoinoculation, or spread to others is a concern. Treat if sexually transmitted to prevent further transmission
  6. Commonly used office-based treatments include curettage, cryotherapy, and topical cantharidin. There is minimal evidence to support efficacy of any one treatment modality
  7. Scarring is possible with both physical and topical treatments and may occur even when lesions are allowed to resolve naturally

What are the causes?

Molluscum contagiosum is caused by a virus. The virus can spread from person to person (is contagious). It can spread through:

  • Skin-to-skin contact with an infected person.
  • Contact with an object that has the virus on it (contaminated object), such as a towel or clothing.
  • Sexual activity.

What increases the risk?

You may be more likely to develop Molluscum contagiosum if you:

  • Live in an area where the weather is moist and warm.
  • Have a weak disease-fighting system (immune system).

What are the symptoms of Molluscum contagiosum?

The main symptom of Molluscum contagiosum is a painless rash that appears 2–7 weeks after exposure to the virus. The rash is made up of small, dome-shaped bumps on the skin. The bumps may:

  • Affect the genitals, thighs, face, neck, or abdomen.
  • Be pink or flesh-colored.
  • Appear one by one or in groups.
  • Range from the size of a pinhead to the size of a pencil eraser.
  • Feel firm, smooth, and waxy.
  • Have a pit in the middle.
  • Itch. For most people, the rash does not itch.

How is this diagnosed?

Molluscum contagiosum may be diagnosed based on:

  • Your symptoms and medical history.
  • A physical exam.
  • Scraping the bumps to collect a skin sample for testing.

How is this treated?

The rash usually goes away within 2 months, but it can sometimes take 6–12 months for it to clear completely. For some people, the rash may go away on its own, without treatment.

In some cases, treatment may be needed to keep the virus from infecting other people or to keep the rash from spreading to other parts of your body. Treatment may also be done if you have anxiety or stress because of the way the rash looks.

If you do need treatment, the options may include:

  • Surgery to remove the bumps by freezing them (cryosurgery).
  • A procedure to scrape off the bumps (curettage).
  • A procedure to remove the bumps with a laser.
  • Putting medicine on the bumps (topical treatment).

Follow these instructions at home:

General instructions

  • Take or apply over-the-counter and prescription medicines only as told by your health care provider.
  • Do not scratch or pick at the bumps. Scratching or picking can cause the rash to spread to other parts of your body.

Preventing infection

As long as you have bumps on your skin, the infection can spread to other people. To prevent this from happening:

  • Do not share clothing or towels with others until the bumps go away.
  • Do not use a public swimming pool, sauna, or shower until the bumps go away.
  • Avoid close contact with others until the bumps go away. This includes sexual contact.
  • Wash your hands often with soap and water. If soap and water are not available, use hand sanitizer.
  • Cover the bumps with clothing or a bandage when you will be near other people.

Contact a health care provider if:

  • The bumps are spreading.
  • The bumps are becoming red and sore.
  • The bumps have not gone away after 12 months.

Additional Info of Molluscum contagiosum

  • Molluscum contagiosum is a benign, self-limited eruption of characteristic umbilicated, papular skin lesions caused by localized poxvirus infection
  • Can occur in any area of the body, but usual pattern varies by age group
    • Children: trunk and proximal extremities
    • Adults: trunk, pubic area, and thighs (sexually transmitted)
  • Infection may be prolonged and severe in people with impaired cell-mediated immunity

Clinical Presentation of Molluscum Contagiosum

History

  • Begins with gradual onset of solitary papules or clusters of papules in characteristic locations
    • In children, papules usually are generalized over trunk and proximal extremities, including axillae, antecubital fossae, popliteal fossae, and inguinal folds
      • Autoinoculation can result in lesions in other areas, including face and eyelids
      • In 10% of childhood cases, genital lesions are present as part of a wider distribution of lesions 
        • When lesions are restricted to genital area only, consider possibility of sexual contact, although such lesions still may be due to autoinoculation
      • Atopic dermatitis is a common comorbidity in affected children
  • In sexually active adolescents and adults, most common in perineum, in inguinal folds, on thighs, and on trunk
  • In patients with untreated HIV, especially those with advanced AIDS, lesions typically involve face (including eyelids) and genitalia
  • Lesions can be completely asymptomatic, or patient may describe itching or burning
  • Resolves spontaneously
    • Individual lesions persist for about 2 months, but the condition overall usually persists for 6 to 9 months 

Physical examination

  • Flesh-colored, dome-shaped, pearly appearing smooth papules with a central umbilication or white core
    • Either solitary lesions or multiple lesions in clusters; may be generalized over large areas
    • Average number of papules is 10 to 20, but ranges anywhere from 1 to several hundred 
    • Lesion size varies; average is 3 to 5 mm but early lesions are smaller 
      • Umbilication may not be visible in earliest lesions
    • Can express a cheesy plug from lesions by squeezing
  • Associated surrounding inflammatory response is often seen in children 
    • Molluscum dermatitis
      • Caused by underlying atopy
      • Skin appears mildly eczematous in areas surrounding individual lesions
    • Inflamed dermatitis
      • Related to the immune response to poxvirus infection
      • Often heralds the onset of spontaneous involution of molluscum lesions
      • Surrounding skin is erythematous, warm, and tender to touch
      • Individual lesions become erythematous and appear swollen; lesions may evolve to pustules
      • Fluctuance may be present
      • Bacterial superinfection can occur
  • Appearance and location of infection in patients with advanced HIV infection (CD4 count less than 100) differs 
    • Commonly involves cheeks, neck, eyelids, and genitalia
    • Giant lesions (larger than 1 cm) can mimic skin cancer 
    • Confluent plaques are often evident
    • Facial disfigurement can occur
    • Oral and genital mucosal lesions may be present

Causes

  • Caused by a poxvirus, types molluscum contagiosum virus 1 to 4 
    • Molluscum contagiosum virus 1 infections are most common in small children
    • Molluscum contagiosum virus 2 infections are most common in patients with HIV
  • Transmission is related to skin-to-skin contact (especially with wet skin) often at the site of mild skin trauma 
    • In some patients, can be fomite transmitted (especially shared towels)
    • Among adults and adolescents, often sexually transmitted
    • In neonates, can be transmitted from the mother’s skin during vaginal delivery; lesions develop in first few months of life

Risk factors of Molluscum Contagiosum

Age
  • Most common in 2 age groups: 
    • Children, especially aged 1 to 4 years
    • Sexually active young adults
Ethnicity/race
  • Occurs worldwide
Other risk factors/associations
  • Immunosuppression
    • Systemic immunosuppression caused by HIV, medications, and malignancy
      • Incidence and severity of molluscum contagiosum in patients with HIV infection is inversely proportionate to the CD4 lymphocyte count 
        • Incidence is 30% in those with CD4 count lower than 100 cells/mL 
  • Abnormal cutaneous immunity, including atopic dermatitis and topical steroid use
    • Prevalence of comorbid atopic dermatitis is higher than in general population 
  • Other associations
    • Although condition is often reported to be associated with use of swimming pools, a prospective study of more than 600 children found no association 
    • Bathing with siblings is associated with a higher number of lesions 
    • Mild skin trauma from removal of pubic hair may be a factor in sexually transmitted infection 

Diagnostic Procedures for Molluscum Contagiosum

Primary diagnostic tools

  • Diagnosis is clinical with recognition of characteristic lesions 
  • If there is no clear central umbilication of lesions, a magnifying lens can be helpful 
  • Rarely, histologic examination of a curetted papule may be necessary if diagnosis is uncertain 
  • Consider possibility of immunodeficiency (eg, advanced HIV infection) if skin lesions are extensive or severe; however, otherwise healthy patients with typical distribution of lesions do not require routine HIV testing 
  • Genital molluscum contagiosum is considered a sexually transmitted disease; test adolescents and adults (and children with suspected inappropriate sexual contact) for other sexually transmitted diseases

Laboratory

  • Histologic examination of a curetted papule reveals a typical microscopic appearance
    • With Wright, Giemsa, Gram, or Papanicolaou stain, microscopy reveals well-circumscribed infected keratinocytes with discrete ovoid intracytoplasmic molluscum bodies 
    • if diagnosis is still uncertain, electron microscopy showing brick-shaped virions can help provide a definitive answer 

Differential Diagnosis of Molluscum Contagiosum

A variety of other skin lesions may visually resemble molluscum contagiosum

Close visual inspection, aided by dermoscopy, can usually differentiate the conditions

If uncertain, the lesion should be biopsied

Most common

Treatment Goals

  • Eradication of infection, either by natural resolution or by elective treatment with a chemical or physical agent

Recommendations for specialist referral

  • Refer to a dermatologist for diagnosis if uncertain, for treatment if lesions are extensive or in cosmetically vulnerable locations, or if patient requests referral
  • Refer patients with eyelid lesions to an ophthalmologist for treatment

Treatment Options

Usually resolves spontaneously without treatment; 2 approaches to management: 

  • Benign neglect approach
    • May consider it for nongenital disease
    • A 2017 Cochrane review concluded that waiting for natural resolution is a reasonable approach, as none of the studied treatments were definitely effective. Studied treatments included: 
      • Cryospray, 5% imiquimod, 10% potassium hydroxide, 10% Australian lemon myrtle oil, 10% benzoyl peroxide cream, 0.05% tretinoin, 5% sodium nitrite, 5% salicylic acid, calcarea carbonica, and 10% povidone-iodine plus 50% salicylic acid plaster 
    • A retrospective review of 170 children failed to show any therapy had a beneficial effect on time to clearance of or rate of recurrence of lesions compared with no therapy 
    • Gentle option is bandage occlusion of lesions while awaiting spontaneous resolution
  • Active treatment approach
    • Patient (or parent) often prefers treatment when there are many lesions to improve cosmesis (especially for facial lesions); to reduce physical symptoms, if present; and to decrease risk of autoinoculation or transmission to others
      • Typically treat molluscum in the perineum to avoid ongoing sexual transmission 
    • A variety of treatments are used despite limited supportive evidence
      • Physical modalities
        • Mechanical curettage, for immediate resolution of lesions
          • In a retrospective study, 70% of children were cured after 1 treatment and an additional 26% after 2 treatments with high satisfaction levels for children and parents 
        • Cryotherapy, particularly for older children and adults
          • In a prospective randomized comparative observer blind study, 100% of patients treated weekly for up to 16 weeks were cured (in comparison with 91.8% treated with imiquimod cream) 
        • Pulsed dye laser
          • Several studies suggest it is safe and effective 
      • Topical treatments
        • Cantharidin (blistering agent)
          • Systematic review found modest benefit in children 
          • Subjective satisfaction is reported, although uncomfortable adverse effects occur in 79% of patients (discomfort/pain and blistering are most common) 
          • Avoid using on face and perineum
          • For in-office treatment only; not for home application
        • Podophyllotoxin, available as podofilox (antimitotic agent)
          • Found to be effective in cream form (not available in United States) in double-blind, placebo-controlled study 
          • May be used, carefully and focally, in perineum; avoid adjacent healthy skin
            • Instruct patient to cleanse skin to remove any residual chemical before intimate skin contact with a partner
        • Imiquimod 5%, cream (immunomodulatory agent)
          • Not recommended, despite being commonly used
            • Cochrane review of 4 placebo-controlled randomized controlled trials of children found the following: 
              • No more effective than placebo in clearing molluscum contagiosum
              • Causes more local adverse effects, including application site reactions
    • Treatment of specific body areas
      • Facial lesions
        • If there are few lesions, can treat them carefully with cryotherapy or curettage, taking care to avoid damage to surrounding skin
          • This can be difficult in young children; consider managing lesions with bandage occlusion while awaiting spontaneous resolution
        • Avoid chemical irritants (eg, cantharidin, podophyllotoxin)
        • Refer patients with eyelid lesions to ocular specialists (eg, ophthalmologist)
      • Lesions in the perineum
        • Commonly treated with curettage or cryotherapy 
        • Podophyllotoxin also is sometimes used, taking care to avoid contact with adjacent skin
          • Instruct patient to remove any residual chemical by cleansing before intimacy
            • Males should use condoms if lesions are on penis
            • Females should use internal condoms (female condoms) if lesions are on vulva
        • Avoid cantharidin in this area
    • Other treatments in use but with minimal supportive evidence
      • Cidofovir cream
        • Cidofovir has been used successfully to treat refractory lesions in patients with HIV and Wiskott-Aldrich syndrome 
      • Oral cimetidine (for its immunomodulatory effects)
        • Oral cimetidine treatment for 2 months (40 mg/kg/day) reduced molluscum contagiosum lesions in the majority of 13 children who had not responded to previous therapy 

For patients with HIV and low CD4 count:

  • Highly active antiretroviral therapy to increase CD4+ cell counts appears to be effective 

Drug therapy

  • Outpatient topical therapy
    • Antimitotic agent
      • Podofilox 0.5% topical gel or topical solution
        • Podofilox 0.5% topical gel or topical solution; Adults: Using the minimum amount to cover the lesion, apply twice daily (morning and evening) with applicator tip for 3 consecutive days, then withhold use for 4 consecutive days. This 1-week cycle may be repeated for 3 more cycles if lesions persist 
        • Podofilox 0.5% topical gel or topical solution; Infants, Children and Adolescents: Safety and efficacy have not been established by the manufacturer. However, guidelines recommend applying twice daily (morning and evening) with applicator for 3 consecutive days, then withholding use for 4 consecutive days
        • Podofilox 0.5% gel may be used in the perianal area. The 0.5% topical solution is not indicated for use in the perianal area

Nondrug and supportive care

Children may attend day care or school, but lesions should be covered 

Procedures
Curettage 

General explanation

  • The epithelial surface of the papule is opened with a sterile needle, scalpel blade, or sharp end of a comedone extractor
  • The core of the lesions is scraped away with a small disposable sharp dermal curette
  • Topical anesthesia can be used, if desired

Indication

  • Elective treatment of molluscum contagiosum lesions
  • Also used to obtain tissue for histologic examination in cases of diagnostic uncertainty
Cryotherapy 

General explanation

  • If using nitrous oxide:
    • Prepare each lesion with a small amount of water-soluble gel
    • Freeze each lesion for 30 to 60 seconds using a very fine-tipped probe to avoid damaging healthy skin
  • If using liquid nitrogen:
    • Freeze each lesion very briefly (several seconds)
    • Lesions should fall completely off within 2 weeks; treat again after that time if they do not

Indication

  • Elective treatment of molluscum contagiosum lesions

Complications

  • Potential for scarring
Cantharidin liquid application 

General explanation

  • Treat in office only. Do not have the patient self-treat at home
  • Not advised for face or perineum
  • Physicians can either have cantharidin compounded by a local pharmacist for use in clinic, or they can purchase it from an independent commercial manufacturer 
    • Not FDA-approved; available commercially as 0.7% cantharidin 
  • Apply with wooden end of a cotton swab directly to the lesion, avoiding surrounding skin
  • Leave on 1 to 6 hours before washing
  • Up to 20 lesions can be treated per session
  • Vesiculation is the expected result

Indication

  • Elective treatment of molluscum contagiosum lesions

Complications

  • Potential for scarring if exuberant blistering occurs

Comorbidities

  • Atopic dermatitis
    • When an eczematous reaction occurs around molluscum contagiosum lesions (very common), treat with low-potency topical steroid 
    • Curettage or cryotherapy are most effective in this population and least likely to exacerbate atopic dermatitis 
    • If planning cantharidin treatment, first treat the atopic dermatitis to decrease risk of significant blistering response 

Complications

  • Scarring
    • May be caused by physical treatments (eg, cryotherapy, curettage) or topical therapies
    • May occur at site of untreated lesions
  • Secondary bacterial infection

Prognosis

  • Self-limited, usually without scarring
    • Does not recur, but reinfection is possible

Prevention

  • Avoid skin-to-skin contact, sharing towels, and bathing with an infected person
  • Use condoms (male and female condoms) if lesions are within the area covered by the condom

Summary

  • Molluscum contagiosum is a skin infection that can cause a rash made up of small, dome-shaped bumps.
  • The infection is caused by a virus.
  • The rash usually goes away within 2 months, but it can sometimes take 6–12 months for it to clear completely.
  • The rash often goes away on its own. However, treatment is sometimes recommended to keep the virus from infecting other people or to keep it from spreading to other parts of your body.

Sources

Lee R et al: Pediatric molluscum contagiosum: reflections on the last challenging poxvirus infection, part 1. Cutis. 86(5):230-6, 2010 Reference

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