Molluscum Contagiosum
Self-limited poxvirus infection producing small dome-shaped umbilicated papules; common in children and immunocompromised adults.
Also known as: molluscum, molluscum contagiosum, MC
Overview
A common cutaneous infection caused by the Molluscum contagiosum virus (MCV), a double-stranded DNA poxvirus. Produces small, dome-shaped, flesh-colored to pearly-white umbilicated papules.
Epidemiology
Worldwide distribution; ~5% prevalence in children. Peak ages 2-5 years and sexually active young adults. Increased prevalence and severity in atopic dermatitis and HIV/immunocompromised.
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Risk factors
- Children in close contact (daycare, siblings, swimming pools, shared towels)
- Atopic dermatitis (impaired barrier, autoinoculation through scratching)
- Sexual contact (genital molluscum in adults)
- Immunosuppression — HIV (particularly when CD4 <100), transplant, biologics; lesions can become large, numerous, and refractory
- Wrestlers, swimmers, gym users
Pathophysiology
MCV is the only poxvirus that infects humans without systemic spread. Infects keratinocytes through microabrasions; replicates entirely in the cytoplasm. Forms characteristic intracytoplasmic inclusion bodies (Henderson-Patterson 'molluscum bodies'). Spread by direct skin contact, fomites, and autoinoculation; incubation 2-7 weeks (range 1 week to 6 months).
Clinical presentation
Symptoms
- Usually asymptomatic; cosmetic concern
- Pruritus from associated dermatitis around lesions ('molluscum dermatitis')
- Tenderness if secondarily infected (BOTE — beginning of the end — sign: erythema and inflammation precedes spontaneous resolution)
Signs / physical exam
- Discrete 2-5 mm (occasionally up to 1-2 cm 'giant molluscum') dome-shaped flesh-colored to pearly-white papules with central umbilication (depression containing white waxy core)
- Distribution in children: trunk, axillae, antecubital and popliteal fossae, face; spares palms and soles
- Distribution in adults: genitalia, lower abdomen, inner thighs (sexually transmitted), or face (after shaving — autoinoculation)
- Eczematous 'molluscum dermatitis' surrounding lesions
- Often grouped or linear from autoinoculation (Koebner)
- Immunocompromised: numerous, large, persistent lesions, often on face
Classic findings
Smooth dome-shaped umbilicated papules with central white waxy core in a child or sexually active adult.
Differential diagnosis
- Verruca (warts) — Verrucous surface, no central umbilication, disrupts skin lines, pinpoint black dots
- Closed comedones (acne) — Smaller, in seborrheic distribution, often with inflammatory acne nearby
- Folliculitis — Erythematous pustules around hair follicles
- Cryptococcosis (HIV) — Molluscum-like papules in advanced HIV (CD4 <100); biopsy/culture differentiates — DERMATOLOGIC EMERGENCY if disseminated
- Histoplasmosis / penicilliosis (immunocompromised) — Molluscum-like papules; geographic exposure; biopsy/culture
- Basal cell carcinoma — Pearly papule with telangiectasias on sun-exposed skin of older adult
- Syringoma / hidrocystoma — Skin-colored periorbital papules; biopsy
Diagnostic workup
Diagnostic criteria
Clinical: characteristic umbilicated papules; dermoscopy and histology in atypical cases.
Labs
- Clinical diagnosis sufficient in most cases
- Dermoscopy: central polylobular yellow-white amorphous structure with crown vessels
- Expression of core onto slide with KOH or stain (Wright, Giemsa) shows Henderson-Patterson bodies
- Biopsy if atypical, atypical site (palms/soles), or to exclude cryptococcosis in HIV
- HIV testing in adults with extensive or facial molluscum without clear risk factor
Imaging
- Not indicated
Diagnostic algorithm
| Setting | Approach |
|---|---|
| Healthy child, asymptomatic | Active observation — resolves in 6-12 months |
| Bothersome / cosmetic / autoinoculating | Cantharidin in office; curettage; berdazimer gel |
| Adult genital molluscum | Treat lesions + screen STIs + counsel partner |
| Eyelid involvement | Refer ophthalmology before destructive therapy |
| Immunocompromised / HIV | Optimize ART; multimodal therapy; biopsy to exclude cryptococcosis |
Treatment
First-line
- Active observation — molluscum is self-limited and resolves spontaneously in healthy children within 6-12 months (occasionally up to 4 years); no scarring
- Cantharidin 0.7% in office — applied to each lesion, covered with tape, washed off in 2-6 hours; produces blister and resolution; well-tolerated in children (avoid face and genitals)
- Berdazimer 10.3% topical gel — FDA-approved 2024 for ages ≥1 year; applied daily × up to 12 weeks
- Cryotherapy (light liquid nitrogen) — quick, can be painful, hypopigmentation risk in skin of color
- Curettage — removes lesion immediately; topical anesthetic before; small risk of scarring
- Topical retinoids (tretinoin 0.05%) for flat lesions
- KOH 10% topical (some studies show efficacy)
- Imiquimod 5% has shown disappointing results in pediatric trials and is no longer recommended
- Treat associated eczematous dermatitis with low-mid potency topical corticosteroid
Sexually transmitted (adult genital)
- Same modalities as cutaneous, plus screen and treat partners
- Counsel on condom use (incomplete protection)
- Screen for other STIs
Immunocompromised (HIV, CD4 <100)
- Initiate or optimize antiretroviral therapy — single most effective intervention
- Combine destructive techniques (curettage, cryotherapy) with topical/systemic agents
- Rule out cryptococcosis and other disseminated mycoses in atypical lesions
Second-line / adjunct
- Intralesional candida antigen, interferon, or cidofovir (topical or IV) for refractory disease in immunocompromised
- Hygiene counseling: avoid sharing towels, swimsuits, baths until resolved; do not pick or scratch lesions
Complications
- Bacterial superinfection from scratching
- Scarring (rare; mostly from destructive treatment)
- Post-inflammatory hyper/hypopigmentation
- Eyelid involvement → conjunctivitis or keratitis (refer to ophthalmology)
- Extensive disease as marker of HIV/immunosuppression
- Eczematous molluscum dermatitis and reactive id reactions
- Sexual transmission stigma and partner concerns in adults
PANCE pearls
- Umbilicated dome-shaped flesh-colored papules in a child = molluscum until proven otherwise.
- BOTE sign (beginning of the end) — sudden inflammation, erythema, and crusting of a molluscum lesion heralds spontaneous resolution; do not treat as bacterial infection.
- Numerous, large, or facial molluscum in an adult should prompt HIV testing — and consider cryptococcosis if CD4 <100.
- Cantharidin is the preferred in-office treatment in pediatrics — painless on application, blister forms hours later.
- Active observation is appropriate and evidence-based for healthy children; aggressive treatment is rarely required.
References
- AAD 2023 — Management of Molluscum Contagiosum (AAD work group review)
- CDC — Molluscum Contagiosum — CDC Poxvirus Branch Clinical Resources
- AAP Red Book 2024 — American Academy of Pediatrics Red Book — Molluscum Contagiosum
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