Molluscum contagiosum

Overview & Definition

Molluscum contagiosum is a common, benign, self-limiting cutaneous infection caused by the molluscum contagiosum virus (MCV) — the only human pathogen of the genus Molluscipoxvirus in the family Poxviridae. It produces firm, dome-shaped, pearly-white papules with a pathognomonic central umbilication containing a curd-like core, distributed variably across the skin of children (trunk, axillae, face, extremities) and adults (frequently the lower abdomen and genitals, where it is sexually transmitted). The natural history in immunocompetent hosts is spontaneous resolution within months to one or two years, which makes watchful waiting a reasonable first-line strategy in the asymptomatic, immunocompetent patient.[1][2][3]

Recognition is high-yield at every exam level — the morphology is pathognomonic, the histology (Henderson-Patterson / molluscum bodies in cup-shaped epidermal down-growths) is uniquely identifiable, and the disease illustrates several transferable themes: a strictly epidermal viral infection with no viraemia, a chronic immunologically-mediated clearance that takes months, the HIV association (extensive, facial, giant, refractory disease as a cutaneous marker of immune failure), and a therapeutic ladder that spans watchful waiting, physical destruction (curettage, cryotherapy, cantharidin), topical agents (KOH, podophyllotoxin, imiquimod, the new nitric-oxide-releasing berdazimer sodium 10.3% gel / Zelsuvmi), and intralesional immunotherapy for refractory disease. Anchoring these threads in MC delivers the broader teaching points of cutaneous infection in one topic.[1][6]

The clinical skill at the bedside is to distinguish the typical lesion from its near-miss mimics (verrucae, closed comedones, milia, basal cell carcinoma, and — in HIV — cryptococcosis), to recognise atypical variants (giant, eczematous, periocular, oral), and to act on the red flags (an adult with extensive disease → test for HIV; a child with genital disease → safeguarding assessment; a periocular lesion with eye symptoms → urgent ophthalmology). [1]

Classification

Molluscum is classified by virus genotype, by lesion morphology, and by clinical context — three axes that change prevalence, prognosis and management: [1]

By virus genotype

Four genotypes are recognised (MCV-1, MCV-2, MCV-3, MCV-4), but MCV-1 causes the great majority of paediatric and adult disease worldwide (~75-95%) and MCV-2 is over-represented in HIV/immunosuppressed adults and in some sexually transmitted cohorts. The genotypes are clinically indistinguishable in the immunocompetent individual; the distinction matters principally for epidemiology and for a small subgroup of immunocompromised patients. No serological immunity cross-protects fully between genotypes, and re-infection is possible.[1][3]

By lesion morphology

• Typical / classic MC — 2-5 mm pearly papules with central umbilication; the commonest form in children.
• Giant MC — single or few lesions over 1 cm (some over 2-3 cm); most often facial in adults; strong association with HIV/immunosuppression; consider biopsy because the differential includes keratoacanthoma and nodular BCC.
• Agminate / clustered MC — multiple lesions grouped in a single region (sometimes linear, from autoinoculation along a scratch).
• Eczema molluscatum (disseminated MC on atopic skin) — widespread lesions arising on the eczematous, excoriated skin of atopic dermatitis; reflects both the Koebner phenomenon and the impaired cutaneous antiviral immunity.
• Inflammatory MC — spontaneously inflamed, crusted or pustular lesions, sometimes resembling a furuncle; a sign of the host immune response beginning to clear the lesion (often a prelude to resolution).
• Pedunculated MC — pedunculated variant, especially on the neck and eyelids; may be confused with skin tags.
• Oral / mucosal MC — uncommon; solitary, umbilicated papules on the lip, buccal mucosa or tongue; seen in HIV and other immunocompromise.
• Periocular / ocular MC — uniquely important because of the risk of follicular conjunctivitis and chronic keratitis. [15]

By clinical context (the dimension that drives management)

[1] [2] [14]

Epidemiology & Risk Factors

Molluscum contagiosum is one of the commonest cutaneous viral infections of childhood worldwide, with an estimated global point prevalence in children of around 5-10% (peaking higher in some tropical regions) and a peak age of 1-10 years. Incidence is bimodal: a primary paediatric peak (1-10 years) driven by skin-to-skin and fomite contact, and a smaller young-adult peak (20-29 years) driven by sexually transmitted genital disease. It accounts for roughly 1% of all dermatology consultations in temperate climates and a higher proportion in the tropics, where it tends to be more florid and more frequently complicated by secondary bacterial infection.[1][3]

Transmission is by three overlapping routes: direct skin-to-skin contact (the dominant route among children and during sexual transmission), fomites (shared towels, sponges, baths, swimming-pool edges, gym equipment, contact-sport mats; the virus is stable for weeks on wet surfaces), and autoinoculation (scratching or picking one lesion seeds new lesions at distant sites — the reason linear and clustered patterns are so common). There is no convincing evidence for airborne or droplet transmission, and viraemia does not occur — the virus is strictly epidermal — so systemic/visceral disease is a feature only of severe immunocompromise.[1][2]

Outbreaks cluster in nurseries, schools, swimming pools, contact-sport teams and shared-bath households. Secondary attack rates in households approach 10-30% when one child is affected; outbreaks in wrestling and gymnastics teams are well recognised. Seasonal variation is weak, with most reports showing a slight summer / swimming-peak excess in temperate regions.[3]

Risk factors for extensive or refractory disease — the high-yield list for any exam: [1]

• Immunosuppression — HIV with low CD4 count is the single most important risk factor for extensive, facial and giant molluscum. In the pre-ART era, facial giant MC was a near-pathognomonic marker of advanced HIV disease; in the ART era it remains a sentinel presentation of uncontrolled HIV or late presentation.
• Iatrogenic immunosuppression — solid-organ transplant recipients, patients on biologics (TNF-alpha inhibitors, IL-17/IL-23 inhibitors, JAK inhibitors), and long-term oral corticosteroids / methotrexate / azathioprine.
• Atopic dermatitis — barrier dysfunction and Th2-dominant cutaneous immunity predispose to widespread eczema molluscatum on eczematous skin.
• Climate — tropical and humid climates favour more florid and secondarily infected lesions.
• Occlusion and maceration — occluded sites (axillae, groin, under a plaster cast) tend to develop more lesions from local autoinoculation. [1]

[1] [2] [3] [14]

Pathophysiology

MCV is a large, enveloped, double-stranded DNA virus (~190 kb genome) of the family Poxviridae, subfamily Chordopoxvirinae, genus Molluscipoxvirus — the only member of that genus to infect humans. Unlike most DNA viruses it replicates entirely in the cytoplasm of infected cells using its own DNA-dependent RNA polymerase, a feature shared with variola and vaccinia but with the unique molluscipoxvirus feature that the virus is almost entirely restricted to the epidermis and does not produce a productive viraemia in immunocompetent hosts.[1][3]

The viral life cycle plays out inside the epidermal keratinocyte, beginning in the basal/suprabasal layer and culminating in massive intracytoplasmic viral factories and inclusions in the more superficial layers. The infected keratinocyte becomes hugely enlarged, its cytoplasm crammed with mature virions packaged into eosinophilic inclusion bodies — the molluscum (Henderson-Patterson) bodies — that compress the nucleus into a thin crescent at the cell periphery. These inclusions enlarge in step with keratinocyte maturation; by the time the cell reaches the granular layer, the inclusion has effectively replaced the cytoplasm. The characteristic central umbilication of the mature lesion is the surface expression of a cup-shaped epidermal down-growth whose core is packed with infected keratinocytes that have ruptured and released their viral inclusions — the curd-like caseous material that can be expressed with lateral pressure.[1][2]

Why the virus stays in the epidermis is the central pathophysiological puzzle and explains much of the disease's behaviour. MCV has evolved an exceptionally large repertoire of immune-evasion proteins, including: [1]

• An IL-18 binding protein (IL-18BP) that neutralises IL-18 (an IFN-gamma-inducing cytokine), blunting the Th1 response.
• Chemokine inhibitors (MC148, MC054, MC007) that competitively bind and sequester host chemokines, impairing recruitment of dendritic cells, NK cells and T-cells to the infected epidermis.
• A glutathione peroxidase (MC066) that neutralises reactive oxygen species and dampens the local oxidative antiviral response.
• Apoptosis inhibitors (MC159, MC160) that delay keratinocyte programmed cell death and prolong the infectious window.
• MHC class I downregulation to evade CD8+ cytotoxic T-cell recognition. [1]

The net effect is a chronic, locally contained infection that the systemic immune system sees but cannot eliminate quickly. Clearance depends ultimately on cell-mediated immunity — when CD4+ and CD8+ T-cells, NK cells and IFN-gamma finally arrive in force, lesions undergo inflammation, crusting and resolution. This explains the strong association with HIV/immunosuppression (no T-cell help → no clearance), the delayed clearance in atopic dermatitis (Th2-skewed local immunity), and the therapeutic effect of intralesional immunotherapy (Candida antigen, PPD, MMR/measles), which calls in a non-specific systemic cell-mediated response that clears the virus at distant, uninjected lesions too.[1][3][12]

Clinical Presentation

The classic lesion is a firm, smooth, dome-shaped, pearly-white or skin-coloured papule, 2-5 mm in diameter (occasionally up to 1-2 cm when "giant"), with a central umbilication from which a curd-like, caseous core can be expressed with lateral pressure. Lesions are usually multiple (10-20 in immunocompetent children, occasionally hundreds in HIV) and may be grouped, linear (from scratching/autoinoculation along a scratch) or scattered. They are typically asymptomatic, although inflammation, crusting and tenderness signal spontaneous resolution; mild pruritus is common, and a surrounding eczematous halo (id reaction / autoeczematisation) occurs in up to 10% of children, especially those with atopy.[1][3]

Site distribution differs sharply between children and adults: [1]

• In children — face, trunk, axillae, extremities, popliteal and antecubital fossae; sparing palms and soles (the thick stratum corneum of the palms and soles is not permissive for MCV). Genital lesions in children are usually the result of autoinoculation from concurrent cutaneous lesions, but sexual abuse must always be considered.
• In adults — the lower abdomen, genitals (penis, vulva, perineum), pubic region and inner thighs in sexually transmitted disease; facial and extremity lesions in immunocompromise.
• In HIV / immunosuppression — extensive (>100 lesions), clustered on the face (especially the beard area, forehead and eyelids) and frequently giant (>1 cm). A typical pattern is dozens-to-hundreds of molluscum on the face, neck and upper trunk of an HIV patient with CD4 below 200 cells/µL.
• In atopic dermatitis (eczema molluscatum) — widespread lesions on eczematous skin, often multiple lesions per eczematous patch; reflects Koebner phenomenon and impaired local antiviral immunity. [1]

The natural history in immunocompetent children is spontaneous resolution in 6-12 months typically, almost always by 2 years; the longest reported individual lesions have persisted for 3-4 years, but this is exceptional. Resolution is often heralded by inflammation, crusting and a pustular or furuncle-like appearance, which indicates that the cell-mediated immune response has finally engaged — this is, paradoxically, a sign that the lesion is on its way out.[1][2][3]

Atypical variants (each is exam-rewarding): [1]

• Giant molluscum — single or few lesions over 1 cm, often facial in HIV; biopsy to exclude keratoacanthoma or nodular BCC.
• Inflammatory molluscum — spontaneously red, swollen and tender; an immune-mediated lesion about to resolve.
• Periorbital molluscum — umbilicated papules on the lid margin that can produce a chronic follicular conjunctivitis, punctate epitheliopathy and, rarely, keratitis with corneal scarring.
• Oral molluscum — umbilicated papules of the lip, tongue or buccal mucosa; reported chiefly in HIV.
• Molluscum of the adult nipple, areola or sole — rare and easily overlooked.
• Conjunctival molluscum — sometimes seen in HIV; the lid lesion is usually the source. [1]

[1] [2] [14] [15]

Differential Diagnosis

The central umbilication of a pearly papule is pathognomonic, but the morphology is mimicked by several conditions that the examiner will probe. The complete differential, with the features that distinguish each: [1]

Other entities that sometimes enter the differential: closed comedones (uniform follicle-based papules without an expressible core), milia (pinpoint keratin cysts, 1-2 mm, no umbilication), sebaceous hyperplasia (yellowish central dot but no umbilication, older adults on the face), syringoma (small skin-coloured papules around the eyes, multiple, no umbilication), folliculitis (yellow-centred pus, not a viral inclusion), xanthoma / xanthelasma (yellow, waxy, on eyelids), lichen planus (violaceous, polygonal, Wickham's striae), fibrous papule of the nose (solitary, dome-shaped, no umbilication), keratoacanthoma (rapidly growing, central keratin plug, but crateriform rather than umbilicated in the classic sense). [1][3]

The id (autoeczematisation) reaction — an itchy, eczematous, sometimes widespread rash on skin distant from the lesions — must be distinguished from secondary bacterial infection (impetiginisation) (yellow crusts, pain, rapidly spreading erythema), scabies (burrows, web-space involvement, family contacts), tinea corporis (annular, scaly, advancing edge), and drug reaction (temporal relation to a new agent). [1]

Clinical & Bedside Assessment

Diagnosis is clinical at the bedside. The bedside sequence is short and reproducible, and is exactly the sequence an OSCE station will test: [1]

1. History — age, duration, number and tempo of new lesions, symptoms (itch, pain, eye irritation, secondary infection), past medical history (atopy, HIV, immunosuppression), medications, family/school contact, and (for adults) sexual history and STI risk.
2. General inspection — count and map the lesions; note distribution, sparing of palms and soles, mucosal/periorbital/genital involvement.
3. Lesion-focused examination — confirm pearly dome, central umbilication, expressible curd-like core (glove-and-gauze expression with lateral pressure is the pathognomonic bedside demonstration); check for surrounding id reaction, secondary bacterial infection, scarring.
4. Dermoscopy (a hand-held dermatoscope is now part of any dermatologist's kit) — the classic molluscum pattern is a central white-yellow amorphous / polylobular structure with a peripheral crown of radial ("dotted" or "comma-shaped") vessels ("crown vessels" or "cloudy coronet sign"); highly specific, useful when the diagnosis is uncertain.
5. Context-driven examination — in an adult with facial or genital disease, examine for HIV stigmata (oral hairy leukoplakia, Kaposi sarcoma, oral candidiasis, generalised lymphadenopathy) and offer HIV and STI testing; in a child with genital lesions, perform a safeguarding-focused examination as per local protocol. [1]

[1] [2] [3]

Investigations

The diagnosis of typical molluscum is clinical — no investigation is required. Investigation is reserved for atypical, solitary, adult, giant, treatment-refractory or immunocompromised presentations, and the investigations chosen depend on the question being asked: [1]

• Dermoscopy — non-invasive, in-clinic; shows the white-yellow amorphous centre with peripheral crown vessels (highly specific; useful when morphology is ambiguous).
• Skin biopsy (rarely needed): indicated for a solitary atypical lesion in an adult (to exclude BCC / keratoacanthoma), giant lesions, or treatment-refractory disease. Histology is pathognomonic — a cup-shaped (lobulated) epidermal down-growth containing intracytoplasmic eosinophilic inclusions (molluscum / Henderson-Patterson bodies) that compress the nucleus to a peripheral crescent; surrounding dermis shows a mixed inflammatory infiltrate once the host response engages.
• Polymerase chain reaction (PCR) for MCV DNA — available in reference laboratories; useful for atypical or HIV-associated disease where confirmation of the genotype (e.g. MCV-2 in HIV) is useful for cohort tracking, and for distinguishing MCV from cutaneous cryptococcosis or histoplasmosis in the immunocompromised host (where biopsies may be sent for both viral PCR and fungal stains).
• Electron microscopy of expressed core — demonstrates the brick-shaped poxvirus particles; a research tool rather than a routine test.
• HIV serology with CD4 count — in any adult with extensive (>50 lesions), facial, giant, genital or refractory molluscum. This is the single highest-yield investigation in this context.
• STI screen — in any adult with genital molluscum (chlamydia and gonorrhoea NAAT, syphilis serology, hepatitis B/C serology, HIV); consider pre-exposure prophylaxis discussion if ongoing risk.
• Baseline immunosuppression review — if the patient is on biologics, immunosuppressive chemotherapy, transplant immunosuppression or oral steroids, involve the responsible team; dose reduction may be appropriate in severe disease.
• FBC, CRP, U&E, LFT, blood glucose / HbA1c — relevant when secondary bacterial infection is suspected, when systemic therapy (oral cimetidine, intralesional immunotherapy) is being considered, and for general pre-treatment assessment. [1]

[1] [3] [4] [15]

Management — Resuscitation

Molluscum is almost never a resuscitation-level disease; the only acute presentations are: [1]

• Severe secondary bacterial infection (impetiginised MC, cellulitis) — treat with oral anti-staphylococcal antibiotics (flucloxacillin; or clarithromycin / doxycycline in penicillin-allergic), topical antiseptics (chlorhexidine washes) and review; this is the standard soft-tissue infection bundle and not specific to MC.
• Periorbital MC with keratitis / visual disturbance — urgent ophthalmology referral for slit-lamp assessment, topical antiviral or antibiotic cover as indicated, and definitive treatment of the lid lesion (typically curettage or surgical excision of the lid-margin papule).
• Extensive MC in a newly diagnosed HIV patient — initiate antiretroviral therapy promptly as part of routine HIV care; do not delay ART for cosmetic MC treatment — restoration of immune function is itself the definitive therapy.
• Anaphylaxis to cantharidin — exceptionally rare but reported; treat as standard anaphylaxis with intramuscular adrenaline. [1]

Beyond these specific scenarios, molluscum is an outpatient disease and the management focus is on the definitive-treatment ladder below. [1]

[1] [7] [11] [15]

Management — Definitive & Stepwise

The decision between watchful waiting and active treatment balances the natural history (self-resolution in 6-12 months in immunocompetent children), the bother to the patient/parent (itch, appearance, contagion concern), the lesion site (face and genitals warrant active treatment because of visibility and transmission risk), the patient cohort (immunocompromised — earlier active treatment), and the treatment burden / adverse-event profile (cantharidin blisters, cryotherapy pain, KOH irritation, scarring from curettage). The 2023 network meta-analysis of treatment efficacy (Chao et al., JDDG) and the 2025 comprehensive treatment review (Ulrych et al., Wiad Lek) provide the modern evidence base.[4][6]

Watchful waiting is appropriate for the immunocompetent, asymptomatic child with non-facial, non-genital, non-bothersome lesions, and is supported by AAP / BAD / AAD guidance. Active treatment is offered for bothersome, spreading, facial, or genital lesions; for parental preference (after counselling); and for any lesion in an immunocompromised patient.[1][3]

Physical destructive methods

The fastest and most reliably effective options; reserved for limited numbers of lesions because of discomfort and (for some techniques) scarring. [1]

• Curettage — highly effective, single-visit clearance for a small number of lesions; requires local anaesthetic (topical EMLA or intralesional lidocaine); small scarring and pigmentary change risk; favoured for facial/genital lesions where rapid clearance matters.
• Cryotherapy (liquid nitrogen) — single or repeated freeze-thaw cycles; effective but painful, with post-treatment vesiculation and pigmentary change; less ideal in children.
• Cantharidin 0.7-0.9% — a topical vesicant that inhibits serine/threonine protein phosphatases, leading to acantholysis and intraepidermal blistering; applied in clinic, washed off by the parent at home in 2-6 hours (recent FDA labelling: 24 hours post-application), producing a small in-office blister that heals in 1-2 weeks. Vakharia 2018 systematic review (Am J Clin Dermatol) confirmed efficacy with a favourable tolerability profile in children; CAMP-1 and CAMP-2 trials (Eichenfield 2022-23) demonstrated superiority over vehicle and led to FDA approval of YCANTH (cantharidin 0.7% topical solution, 2023) — the first FDA-approved specific treatment for molluscum. Apply with care to avoid normal skin; not for use near the eyes or on mucosal surfaces.[7][8][11]
• Pulsed dye laser (PDL) and CO2 laser — selective vascular or ablative destruction; used in refractory or cosmetically important lesions; specialist treatment.

Topical agents

• Berdazimer sodium 10.3% gel (Zelsuvmi) — a nitric-oxide-releasing topical agent; FDA-approved (2024) for molluscum on the basis of the B-SIMPLE phase 3 trials (Browning et al., JAMA Dermatology 2022) showing significantly higher clearance rates vs vehicle. Applied once daily, gentle inflammatory reaction is the main adverse event. [9][10]
• Potassium hydroxide (KOH) 5-10% — applied to lesions daily until inflammation / crusting develops; widely used parent-applied topical in paediatric MC; mild irritant dermatitis is the main adverse event.
• Imiquimod 5% cream — an immune-response modifier (TLR-7 agonist) that induces local IFN-alpha and Th1 cytokines; variable efficacy in randomised trials (some showing no benefit over vehicle in immunocompetent children); can produce significant local inflammation and is no longer first-line for routine paediatric MC but has a role in extensive or refractory disease. [1]
• Podophyllotoxin 0.5% (self-applied) — antimitotic; self-applied for genital MC in non-pregnant adults; contraindicated in pregnancy, breastfeeding, and children.
• Topical cidofovir — used off-label in HIV/immunocompromised hosts with refractory disease.
• Tea tree oil (Melaleuca alternifolia) 10% and benzoyl peroxide — modest evidence for symptomatic benefit (Kairey 2023 systematic review); common contact irritant. [13]
• Tretinoin 0.1% / adapalene 0.1% — small observational studies suggest benefit by inducing local inflammation and desquamation.
• Salicylic acid (wart paints) — occasionally used as adjunct; less effective than for HPV warts.

Intralesional immunotherapy

A specific specialist approach for refractory or extensive molluscum: intradermal injection of an immunogenic antigen into one or a few index lesions recruits a systemic cell-mediated immune response that clears both injected and distant, uninjected lesions — a phenomenon reminiscent of the "primary and secondary lesion" response seen with intralesional Candida antigen in viral warts. The antigens used are Candida albicans antigen (most evidence), trichophytin, BCG, PPD, and MMR / measles antigen. Wells 2020 systematic review (Dermatologic Therapy) confirmed efficacy and a favourable safety profile; injection-site reaction and post-inflammatory pigment change are the main adverse events; flu-like symptoms can occur. [12]

Molluscum in immunocompromise

In HIV the cornerstone is restoration of immune function with antiretroviral therapy (ART) — facial/giant molluscum characteristically clears as CD4 counts rise. ART should be initiated promptly; adjunctive therapies (topical cidofovir, imiquimod, cantharidin, curettage, intralesional immunotherapy) accelerate clearance but cannot substitute for immune reconstitution. Co-existing opportunistic infection must be excluded when lesions are atypical (persistent ulceration, necrotic centres, associated systemic symptoms) by biopsy, fungal stains and tissue culture. The standard HIV-dermatology differential — cryptococcosis, histoplasmosis, Penicillium marneffei, bacillary angiomatosis, Kaposi sarcoma — must remain in mind. [14]

In iatrogenic immunosuppression (biologics, transplant immunosuppression), discussion with the responsible team about dose reduction or holiday may be appropriate; many biologics can be continued safely during active treatment of MC.[1]

Oral cimetidine in paediatric molluscum

Oral cimetidine (an H2-antihistamine with weak immunomodulatory activity at high dose) has been used in paediatric MC at 40 mg/kg/day in divided doses for 2-3 months; evidence is mixed and inferior to physical destructive methods, but it remains a parent-friendly option in children who cannot tolerate destructive treatment. Avoid in patients on drugs metabolised by CYP (cimetidine inhibits CYP-mediated metabolism). [1]

General measures and counselling

• Avoid sharing towels, sponges, and personal items; cover lesions where practical.
• Discourage scratching to limit autoinoculation; trim fingernails.
• Swimming pools — most current guidance allows swimming with covered lesions; a waterproof dressing is reasonable.
• School / nursery exclusion — not necessary in most guidelines (transmission requires close skin contact, not casual proximity); some institutions adopt a more conservative line; individualised.
• Counsel on sexual transmission in genital MC in adults and screen for other STIs. [1]

[1] [1] [2] [3] [4] [6] [7] [8] [10] [11] [12] [13] [14]

Specific Subtypes & Scenarios

Paediatric molluscum

The commonest demographic; peak age 1-10 years. Skin-to-skin and fomite transmission dominate; autoinoculation explains the linear/clustered patterns. Natural history: self-resolution in 6-12 months in the majority, 70-90% by 2 years; longer courses in atopic dermatitis. First-line management: reassurance, watchful waiting, parental counselling, with active treatment reserved for bothersome / facial / spreading lesions or parental preference. Cantharidin (in-clinic) or KOH (parent-applied) are the most popular active paediatric treatments. [1][2]

Genital molluscum in adults — STI

In sexually active adults, genital MC is a sexually transmitted infection. Co-existing STI testing is mandatory (chlamydia NAAT, gonorrhoea NAAT, syphilis serology, HIV, hepatitis B/C); partner notification should be discussed; consistent condom use reduces transmission; HPV co-infection is common. Treatment: podophyllotoxin self-applied, or curettage/cryotherapy/cantharidin for clinician-applied options. Genital MC in a child, however, is more often autoinoculation from concurrent cutaneous lesions than sexual abuse — but safeguarding assessment is mandatory in any prepubertal child with genital MC. Involve paediatrics and child protection according to local protocol.[1][5]

Eczema molluscatum (MC on atopic dermatitis)

Widespread MC on eczematous skin reflects both Koebner phenomenon (lesions arising on damaged skin at sites of scratching) and impaired cutaneous antiviral immunity. The skin barrier defect and Th2-dominant microenvironment favour viral replication. Management has two parallel tracks: control the underlying eczema (emollients, topical corticosteroids, topical calcineurin inhibitors, anti-IL-4Rα biologics in severe cases) and treat the MC actively (cantharidin, curettage or KOH; intralesional immunotherapy in extensive disease). Be cautious using potent topical steroids on inflamed MC lesions without addressing the virus simultaneously. [1]

Giant molluscum

Solitary or few lesions over 1 cm in diameter; predominantly seen in HIV/immunosuppressed adults, often on the face. The principal reason for biopsy in a "molluscum-like" lesion is to exclude keratoacanthoma, nodular BCC, or amelanotic melanoma; giant MC may also ulcerate or become pedunculated. Management is by excision or aggressive destructive treatment; underlying immunocompromise (especially HIV) must be excluded. [14]

Periorbital / ocular molluscum

The lid-margin umbilicated papule is a small but important variant because of the proximity to the conjunctiva and cornea. Reported complications include chronic follicular conjunctivitis, punctate epitheliopathy, keratitis with corneal scarring, and pannus. Treatment is by ophthalmology-guided curettage or surgical excision of the lid lesion; cantharidin is contraindicated near the eye. Topical therapies should not be applied periocularly. A retrospective 20-year systematic review (Naseer et al., Int Ophthalmol Clin 2025) confirmed the spectrum of ocular involvement. [15]

Molluscum in HIV / advanced immunosuppression

A sentinel cutaneous manifestation of uncontrolled HIV. Typically extensive, facial (beard area, forehead, eyelids), often giant, frequently refractory to destructive therapy alone. The cornerstone is ART — clearance often follows CD4 reconstitution. Adjunctive destructive / topical therapy accelerates clearance; disseminated or atypical lesions warrant biopsy to exclude opportunistic infections (cryptococcosis, histoplasmosis, Penicillium marneffei, bacillary angiomatosis). In iatrogenic immunosuppression (biologics, transplant recipients), discuss dose modification with the responsible team. [14]

Oral / mucosal / plantar molluscum

Rare but recognised, particularly in HIV. Oral lesions — small, umbilicated papules on the lip, buccal mucosa or tongue; biopsy if atypical. Plantar lesions — uncommon because of thick stratum corneum; chronic pressure points can produce lesions with a different morphology (deep, endophytic, keratotic); biopsy if doubtful. [1][3]

[1] [2] [3] [14] [15]

Complications & Pitfalls

Disease-related complications [1]

• Secondary bacterial infection (impetiginisation) — Staphylococcus aureus or Streptococcus pyogenes superinfection of excoriated lesions; treat with topical antiseptics and oral anti-staphylococcal antibiotics.
• Eczematous id (autoeczematisation) reaction — a delayed-type hypersensitivity response to viral antigens producing an eczema-like rash in a symmetric pattern at sites distant from the lesions; can be widespread, itchy and steroid-responsive; does not in itself imply secondary infection.
• Conjunctivitis and keratitis — periocular/ocular MC; refer to ophthalmology.
• Scarring — from the natural history of lesions or from destructive treatment.
• Psychosocial impact — particularly with extensive or facial disease.
• Disseminated MC in HIV — a marker of advanced immunosuppression with associated opportunistic infection risk.
• Autoinoculation — responsible for the linear and clustered patterns; discouraged by trimming nails and treating itch. [1]

Treatment-related complications [1]

• Cantharidin — vigorous blistering if applied to normal skin, contact dermatitis, transient pigment change, ring-shaped scarring (uncommon); avoid periocular / mucosal use.
• Cryotherapy — pain, blistering, hypopigmentation or hyperpigmentation, scarring (especially with freeze times >10 s).
• Curettage — pain, bleeding, infection, scarring.
• Imiquimod — intense local inflammation, flu-like symptoms (uncommon), hypopigmentation.
• KOH — irritant contact dermatitis; avoid normal skin.
• Berdazimer — local inflammation, mild application-site reactions.
• Intralesional immunotherapy — injection-site inflammation, post-inflammatory pigment change, flu-like symptoms. [1]

Classic examiner pitfalls [1]

1. Mistaking a solitary umbilicated papule on an adult face for molluscum when it is a BCC or keratoacanthoma — biopsy if the diagnosis is uncertain, especially in sun-exposed skin in an adult.
2. Failing to test for HIV in an adult with extensive, facial, genital or refractory MC.
3. Missing safeguarding in a prepubertal child with genital MC — although autoinoculation is the commonest cause, sexual abuse must be actively excluded; involve paediatrics and child protection.
4. Missing concomitant STIs in an adult with genital MC.
5. Treating id reaction as secondary bacterial infection — inappropriate antibiotics.
6. Applying cantharidin periocularly — risk of corneal involvement; treat periocular MC only with ophthalmology input.
7. Using podophyllotoxin in a pregnant patient — teratogenic; avoid.
8. Premature discontinuation of ART response — facial/giant MC takes months to clear after immune reconstitution. [1]

[1] [2] [7] [14] [15]

Prognosis & Disposition

In immunocompetent children, the prognosis is excellent; 70-90% spontaneously resolve within 2 years, with a median time-to-clearance of 6-12 months. Prolonged disease correlates with atopic dermatitis, immunosuppression, HIV and treatment delay. Recurrence is common because the virus is ubiquitous in the community and re-infection with the same or a different genotype can occur after clearance; reinfection does not imply treatment failure. [1]

In HIV, the prognosis depends on immune reconstitution. With consistent ART, facial/giant MC characteristically improves as CD4 counts rise; without ART, lesions can persist for years and may be both cosmetically and psychologically disabling. [1]

Disposition — almost always outpatient. Dermatology referral is appropriate for: atypical/uncertain diagnosis, giant lesions, extensive/facial/immunocompromised disease, treatment-refractory lesions, and periorbital involvement (co-management with ophthalmology). [1]

Follow-up — pragmatic and proportionate. A 3-6 month review is appropriate for watchful-waiting cases to confirm resolution or discuss escalation; active treatment cases are reviewed every 4-8 weeks until clearance. Patients and parents should be safety-netted to return if there is redness, swelling or pus around a lesion (secondary infection), eye involvement, new genital lesions in an adult, rapid spread, or failure to resolve within 1-2 years in immunocompetent children (which should prompt re-examination and consideration of biopsy or further investigation). [1][2][3]

Special Populations

Paediatric

Watchful waiting is appropriate in most asymptomatic, non-facial, non-genital cases. Active treatment options with the most paediatric data are cantharidin (YCANTH) and curettage (in older children under local anaesthetic); KOH is widely used parent-applied. School exclusion is not routinely required. The child should be reviewed at 3-6 months and parents warned about autoinoculation (fingers and towels). In a child with genital MC, safeguarding assessment is mandatory (and in most paediatric cases autoinoculation is the cause); involve paediatrics and child protection per local protocol. [1]

Pregnancy

Molluscum in pregnancy is uncommon and usually self-resolves. Podophyllotoxin is contraindicated (teratogenic). Curettage under local anaesthetic, cryotherapy, and cantharidin are reasonable; imiquimod is generally avoided (limited safety data). [1]

Elderly

Molluscum is uncommon in the elderly; a new umbilicated papule is more often a BCC, sebaceous hyperplasia, or keratoacanthoma and warrants biopsy. In frail elderly on long-term immunosuppression, MC can be more extensive and persistent; management is supportive and conservative. [1]

HIV / iatrogenic immunosuppression

Discussed above. ART in HIV, dose modification / specialist discussion in transplant and biologic immunosuppression, and consideration of intralesional immunotherapy for refractory disease. Extensive facial/giant MC is a sentinel for advanced immunosuppression and warrants opportunistic-infection screening. [14]

Atopic dermatitis

Widespread MC ("eczema molluscatum") on the eczematous, excoriated skin. Two-track management: control the eczema (emollients, topical anti-inflammatories, biologic therapy where appropriate) and treat MC actively. Be alert to bacterial superinfection (most atopic patients are colonised by S. aureus). [1]

Evidence, Guidelines & Regional Differences

Landmark evidence and regulatory approvals: [1]

• CAMP-1 and CAMP-2 trials (Eichenfield LF et al., 2022-23) — phase 3 RCTs of cantharidin 0.7% topical solution (later YCANTH) vs vehicle in paediatric molluscum; YCANTH demonstrated significantly higher complete clearance rates (~50% vs ~15% for vehicle at week 12) with a tolerable adverse-event profile (local blistering, application-site pain), leading to FDA approval in 2023 as the first specific pharmacological therapy for molluscum. [8][11]
• B-SIMPLE phase 3 trials (Browning JC et al., JAMA Dermatology 2022) — RCTs of berdazimer sodium 10.3% gel (later Zelsuvmi) vs vehicle; the active arm achieved complete clearance in ~30-40% (vs ~20% vehicle) at week 12 with once-daily application, mild application-site reactions; FDA approval in 2024 for the treatment of molluscum contagiosum. [10]
• Network meta-analysis (Chao YC et al., JDDG 2023) — comparative efficacy of available treatments; ranked cantharidin, curettage and berdazimer among the top performers for both clearance and patient satisfaction; older agents (imiquimod, KOH, herbal) showed more variable benefit. [6]
• Comprehensive treatment review (Ulrych JM et al., Wiad Lek 2025) — synthesis of the modern treatment landscape.
• Intralesional immunotherapy for molluscum (Wells A et al., Dermatologic Therapy 2020) — systematic review confirming benefit; Candida antigen and MMR antigen the most used. [12]

Guideline bodies: [1]

• American Academy of Dermatology (AAD) — endorses watchful waiting as a reasonable first approach in immunocompetent children; acknowledges cantharidin, KOH, imiquimod and curettage as options.
• American Academy of Pediatrics (AAP) — supports watchful waiting and emphasises that exclusion from school is not necessary.
• British Association of Dermatologists (BAD) — endorses active treatment for bothersome disease; recognises cantharidin (US) and intralesional immunotherapy (specialist UK centres).
• Indian Association of Dermatologists (IADVL) — emphasises affordability and access: KOH, curettage and watchful waiting are first-line; intralesional immunotherapy and YCANTH restricted to centres with expertise / cost coverage.
• Australian (ACN/PBAD) and EU guidance is broadly concordant with US/UK practice. [1]

Regional differences in practice: [1]

[1] [1]

Where evidence remains weak: [1]

• Imiquimod efficacy in children — historical RCTs of imiquimod for paediatric MC show variable benefit; not first-line in current practice.
• Oral cimetidine in children — early reports suggested benefit, but more recent controlled data show limited efficacy.
• Tea tree oil — modest benefit; significant contact irritant dermatitis in some.
• Intralesional immunotherapy — strong case-series evidence but few placebo-controlled trials; remains an option for refractory disease. [1]

[1] [2] [3] [4] [6] [7] [8] [10] [11] [12]

Exam Pearls

1. Pearly papule + central umbilication + curd-like core is pathognomonic; histology shows Henderson-Patterson (molluscum) bodies in a cup-shaped epidermal down-growth.
2. MCV is a poxvirus (genus Molluscipoxvirus) — replicates in cytoplasm; no viraemia; cleared by cell-mediated immunity over months.
3. Sparing palms and soles; distribution: trunk/axillae in children, genitals in sexually active adults.
4. Natural history: self-resolution in 6-12 months in 70-90%, almost always by 2 years — watchful waiting is first-line in the asymptomatic immunocompetent child.
5. Treatment ladder: curettage / cryotherapy / cantharidin (YCANTH 0.7%) → KOH / podophyllotoxin (genital) / imiquimod / berdazimer 10.3% gel (Zelsuvmi) → intralesional immunotherapy (Candida, PPD, MMR).
6. YCANTH (cantharidin 0.7%) — FDA-approved 2023; applied in clinic, washed off at 24 h; small blister; high efficacy and tolerability in children.
7. Zelsuvmi (berdazimer 10.3% gel) — FDA-approved 2024; nitric-oxide-releasing topical; B-SIMPLE phase 3 evidence.
8. Genital MC in adult = STI — STI screen, partner notification, condoms. Genital MC in child — autoinoculation is commonest, but safeguarding assessment is mandatory.
9. Extensive, facial, or giant MC in an adult → think HIV — test; ART is the cornerstone.
10. Periorbital MC with eye symptoms → urgent ophthalmology — risk of chronic conjunctivitis and keratitis.
11. Atopic dermatitis + MC = eczema molluscatum — Koebner phenomenon; treat both the eczema and the virus.
12. Id (autoeczematisation) reaction — eczema-like rash distant from the lesions; cell-mediated; responds to topical steroids (not antibiotics).
13. Podophyllotoxin is contraindicated in pregnancy (teratogenic) and in prepubertal children.
14. Imiquimod efficacy in paediatric MC is variable — not first-line; largely superseded by cantharidin and berdazimer.
15. Network meta-analysis 2023 ranks cantharidin, curettage and berdazimer favourably; imiquimod shows variable benefit. [1]

1. Hebert AA, Bhatia N, Del Rosso JQ. Molluscum Contagiosum: Epidemiology, Considerations, Treatment Options, and Therapeutic Gaps. *J Clin Aesthet Dermatol* 2023
2. Leung AKC, Barankin B, Hon KLE. Molluscum Contagiosum: An Update. *Recent Pat Inflamm Allergy Drug Discov* 2017
3. Meza-Romero R, Navarrete-Dechent C, Downey C. Molluscum contagiosum: an update and review of new perspectives in etiology, diagnosis, and treatment. *Clin Cosmet Investig Dermatol* 2019
4. Ulrych JM, Krupa J, Malinowski M, et al. Molluscum contagiosum: a comprehensive review of treatment modalities. *Wiad Lek* 2025
5. Stulberg DL, Hutchinson AG. Molluscum contagiosum and warts. *Am Fam Physician* 2003
6. Chao YC, Ko MJ, Tsai WC, et al. Comparative efficacy of treatments for molluscum contagiosum: A systematic review and network meta-analysis. *J Dtsch Dermatol Ges* 2023
7. Vakharia PP, Chopra R, Silverberg NB, et al. Efficacy and Safety of Topical Cantharidin Treatment for Molluscum Contagiosum and Warts: A Systematic Review. *Am J Clin Dermatol* 2018
8. Gupta AK, Mann A, Vincent K, et al. YCANTH (Cantharidin) Topical Solution. *Skinmed* 2023
9. Gupta AK, Mann A, Vincent K, et al. Zelsuvmi (Berdazimer) Topical Gel. *Skinmed* 2024
10. Browning JC, Enloe C, Cartwright M, et al. Efficacy and Safety of Topical Nitric Oxide-Releasing Berdazimer Gel in Patients With Molluscum Contagiosum: A Phase 3 Randomized Clinical Trial. *JAMA Dermatol* 2022
11. Ogilvie-Turner K, Goldman RD. Cantharidin for molluscum contagiosum. *Can Fam Physician* 2020
12. Wells A, Saikaly SK, Schoch JJ. Intralesional immunotherapy for molluscum contagiosum: A review. *Dermatol Ther* 2020
13. Kairey L, Agnew T, Bowles EJ, et al. Efficacy and safety of Melaleuca alternifolia (tea tree) oil for human health — A systematic review of randomized controlled trials. *Front Pharmacol* 2023
14. Mohseni Afshar Z, Goodarzi A, Emadi SN, et al. A Comprehensive Review on HIV-Associated Dermatologic Manifestations. *Int J Microbiol* 2023
15. Naseer S, Mian SI, Hakim FE. Ocular and Periorbital Manifestations of Molluscum Contagiosum: A 20-year Systematic Review. *Int Ophthalmol Clin* 2025
16. Clebak KT, Malone MA. Skin Infections. *Primary Care* 2018

Exam application bank (NEET-PG / INICET)

One-line answer

Molluscum contagiosum (MC) is a common, self-limiting cutaneous infection caused by the molluscum contagiosum virus (MCV), a member of the Poxviridae family. It presents as 2-5 mm firm, dome-shaped, pearly papules with a pathognomonic central umbilication containing a curd-like core, distributed on the trunk and axillae in children and the lower abdomen/genitals in sexually active adults. Predominant in young children (peak 1-10 years), it is transmitted by direct skin contact, fomites and autoinoculation; genital disease in adults is sexually transmitted and genital disease in children requires a safeguarding assessment. In HIV and atopic dermatitis the disease can be extensive, giant or 'eczema-molluscatum'. Diagnosis is clinical; dermoscopy shows the characteristic crown vessels. Most lesions resolve spontaneously over 6-12 months in immunocompetent hosts, and active treatment options

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Molluscum contagiosum.

References

1. [1]Hebert AA, Bhatia N, Del Rosso JQ. Molluscum Contagiosum: Epidemiology, Considerations, Treatment Options, and Therapeutic Gaps J Clin Aesthet Dermatol, 2023.PMID 37636018
2. [2]Leung AKC, Barankin B, Hon KLE. Molluscum Contagiosum: An Update Recent Pat Inflamm Allergy Drug Discov, 2017.PMID 28521677
3. [3]Meza-Romero R, Navarrete-Dechent C, Downey C. Molluscum contagiosum: an update and review of new perspectives in etiology, diagnosis, and treatment Clin Cosmet Investig Dermatol, 2019.PMID 31239742
4. [4]Ulrych JM, Krupa J, Malinowski M, et al. Molluscum contagiosum: a comprehensive review of treatment modalities Wiad Lek, 2025.PMID 40847879
5. [5]Stulberg DL, Hutchinson AG. Molluscum contagiosum and warts Am Fam Physician, 2003.PMID 12674451
6. [6]Chao YC, Ko MJ, Tsai WC, et al. Comparative efficacy of treatments for molluscum contagiosum: A systematic review and network meta-analysis J Dtsch Dermatol Ges, 2023.PMID 37199262
7. [7]Vakharia PP, Chopra R, Silverberg NB, et al. Efficacy and Safety of Topical Cantharidin Treatment for Molluscum Contagiosum and Warts: A Systematic Review Am J Clin Dermatol, 2018.PMID 30097988
8. [8]Gupta AK, Mann A, Vincent K, et al. YCANTH(TM) (Cantharidin) Topical Solution Skinmed, 2023.PMID 37945366
9. [9]Gupta AK, Mann A, Vincent K, et al. Zelsuvmi(TM) (Berdazimer) Topical Gel Skinmed, 2024.PMID 39748580
10. [10]Browning JC, Enloe C, Cartwright M, et al. Efficacy and Safety of Topical Nitric Oxide-Releasing Berdazimer Gel in Patients With Molluscum Contagiosum: A Phase 3 Randomized Clinical Trial JAMA Dermatol, 2022.PMID 35830173
11. [11]Ogilvie-Turner K, Goldman RD. Cantharidin for molluscum contagiosum Can Fam Physician, 2020.PMID 32532721
12. [12]Wells A, Saikaly SK, Schoch JJ. Intralesional immunotherapy for molluscum contagiosum: A review Dermatol Ther, 2020.PMID 33044025
13. [13]Kairey L, Agnew T, Bowles EJ, et al. Efficacy and safety of Melaleuca alternifolia (tea tree) oil for human health-A systematic review of randomized controlled trials Front Pharmacol, 2023.PMID 37033604
14. [14]Mohseni Afshar Z, Goodarzi A, Emadi SN, et al. A Comprehensive Review on HIV-Associated Dermatologic Manifestations: From Epidemiology to Clinical Management Int J Microbiol, 2023.PMID 37496761
15. [15]Naseer S, Mian SI, Hakim FE. Ocular and Periorbital Manifestations of Molluscum Contagiosum: A 20-year Systematic Review Int Ophthalmol Clin, 2025.PMID 40116404
16. [16]Clebak KT, Malone MA. Skin Infections Prim Care, 2018.PMID 30115333