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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Question 1DermatologyMedium
A 28-year-old male has multiple firm, flesh-colored papules with central umbilication scattered over his trunk, arms, and face — some are larger than 1cm. CD4 is 45. He has no HIV treatment currently. Which of the following is the most likely diagnosis?
AFolliculitis
BKeratoacanthoma
CMolluscum contagiosum
DVerruca vulgaris
ECryptococcal skin lesions
Reveal answer & full explanation
Correct answer: C — Molluscum contagiosum
AFolliculitis
BKeratoacanthoma
CMolluscum contagiosum✓
DVerruca vulgaris
ECryptococcal skin lesions
Why Molluscum contagiosum is correct
Molluscum contagiosum is a poxvirus transmitted by skin-to-skin contact or fomites
In immunocompetent hosts it appears as 3-6mm dome-shaped umbilicated papules, self-limited over 6-18 months
In AIDS (CD4 below 50): widespread, confluent, and giant lesions (above 1cm) resistant to local therapy — as seen in this patient
Diagnosis is clinical (central umbilication) or by Giemsa/H&E stain showing Henderson-Paterson bodies (viral inclusion bodies)
Why the others are wrong
Cryptococcal skin lesions — can mimic molluscum but would be confirmed by culture or staining for encapsulated yeast, not Henderson-Paterson bodies (confused-with mimic)
Folliculitis — presents as follicular-based pustules, not umbilicated papules (right-region-wrong-lesion)
Verruca vulgaris — HPV-induced hyperkeratotic papules with a rough surface and pinpoint black dots (thrombosed capillaries), not smooth dome-shaped papules with central umbilication (confused-with wart)
Keratoacanthoma — a firm dome-shaped nodule with a central keratin-filled crater can resemble a giant umbilicated molluscum, but it is usually a solitary, rapidly growing lesion on sun-exposed skin of older adults, not multiple papules scattered over the trunk, arms, and face (confused-with central crater)
Additional high-yield points
Treatment: (1) antiretroviral therapy (ART) is most effective — immune reconstitution leads to spontaneous resolution; (2) local therapies: cryotherapy, curettage, trichloroacetic acid, cantharidin (blistering agent — most effective topical), potassium hydroxide; imiquimod is less effective in immunocompromised
Without immune restoration (ART), local treatments have high recurrence rates
Facial molluscum in an HIV patient is often a clinical marker of CD4 below 200, but molluscum is not an AIDS-defining condition
Question 2DermatologyMedium
A 4-year-old boy is brought in by his mother, who noticed several small bumps on his trunk and right axilla over the past 6 weeks. He is otherwise healthy, attends daycare, and takes no medications. He has no pain or itching. On examination there are about eight discrete 2-4 mm dome-shaped, flesh-colored papules with central umbilication; the surrounding skin is normal and there is no erythema or drainage. The lesions spare the palms, soles, face, and genitals. Which of the following is the most appropriate initial management?
ADaycare exclusion until lesions clear
BActive observation and reassurance
CCryotherapy with liquid nitrogen
DNightly topical imiquimod 5% cream
EIn-office cantharidin application
Reveal answer & full explanation
Correct answer: B — Active observation and reassurance
ADaycare exclusion until lesions clear
BActive observation and reassurance✓
CCryotherapy with liquid nitrogen
DNightly topical imiquimod 5% cream
EIn-office cantharidin application
Why Active observation and reassurance is correct
Molluscum contagiosum is a self-limited poxvirus infection that resolves spontaneously in healthy children, typically within 6-12 months without scarring.
This child has few, asymptomatic, uncomplicated lesions and no immunocompromise, so watchful waiting plus parental reassurance is the evidence-based first-line approach.
Active intervention is reserved for symptomatic, extensive, cosmetically distressing, or anogenital lesions, or for immunocompromised hosts.
Why the others are wrong
In-office cantharidin application - a legitimate and often-preferred pediatric destructive therapy, but it is a step beyond what an asymptomatic well child with a handful of lesions needs initially.
Daycare exclusion until lesions clear - the AAP advises against excluding children with molluscum from child care or school; lesions can persist for months, and keeping them covered by clothing and not sharing towels or bath items is enough to limit spread.
Cryotherapy with liquid nitrogen - a real molluscum treatment, but it is painful, poorly tolerated by young children, and carries hypopigmentation and scarring risk.
Nightly topical imiquimod 5% cream - an immune-response modifier familiar from genital warts and once used off-label for molluscum, but randomized pediatric trials found it no more effective than vehicle and it causes local skin reactions, so it is not recommended; a well child with a few asymptomatic lesions needs no treatment at all.
Additional high-yield points
When treatment is chosen, options include cantharidin, curettage, cryotherapy, and topical berdazimer gel; curettage is effective but painful and usually requires topical anesthesia.
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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 (sole member of genus Molluscipoxvirus) is the only circulating poxvirus for which humans are the sole natural host; infection stays confined to the epidermis 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, purulence, or spreading erythema if secondarily infected; distinguish from the BOTE (beginning of the end) sign, a sterile inflammatory flare that precedes spontaneous resolution and needs no antibiotics
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)
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
Molluscum contagiosum management by clinical setting.
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 (YCANTH, FDA-approved 2023 for age ≥2) — applied to each lesion without occlusion, washed off with soap and water at 24 hours (sooner if severe blistering), repeated every 3 weeks as needed; 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)
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; no exclusion from child care, school, or swimming is needed (AAP) — cover exposed lesions with clothing or a watertight bandage
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.
Imiquimod 5% is not recommended for molluscum — it was no better than vehicle in two pediatric randomized trials.
References
Forbat 2017 — Molluscum Contagiosum: Review and Update on Management (Forbat, Al-Niaimi, and Ali, Pediatr Dermatol 2017;34(5):504-515)
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