Molluscum Contagiosum: Pearly Bumps in Children and Adults

Clinical Overview

Molluscum contagiosum represents a common viral infection caused by a large DNA poxvirus that produces characteristic pearly, dome-shaped, umbilicated papules affecting skin and occasionally mucous membranes. The condition is highly contagious through direct contact with infected individuals or contaminated fomites, accounting for significant disease burden in pediatric populations and sexually active adults. Lesions typically appear 2-8 weeks following exposure to infected individuals or contaminated materials including clothing, towels, or shared grooming implements. Molluscum contagiosum typically demonstrates self-limited clinical course lasting 6-24 months without treatment, though many patients and parents seek treatment to accelerate resolution and prevent transmission to contacts. The characteristic morphology of umbilicated papules appearing in crops or clusters distinguishes molluscum from other infectious papules. Individual lesions range from 2-5 millimeters in diameter, though larger lesions can develop with chronicity or immunosuppression. Pruritus frequently accompanies molluscum contagiosum, particularly with secondary infection or inflammatory response, creating risk of autoinoculation and spread. Immunocompromised individuals including HIV-positive patients with CD4 less than 50 cells/microliter may develop extensive, widespread involvement with numerous larger lesions that prove highly resistant to therapy.

Epidemiology

Molluscum contagiosum demonstrates worldwide distribution with varying prevalence based on geographic region, climate, and age group. Peak incidence occurs in children aged 2-5 years, with prevalence of 0.2-12% in healthy children depending on geographic region and socioeconomic factors. Prevalence is higher in warm, humid climates and in developing nations. Secondary peak occurs in sexually active adults, with estimated prevalence of 0.1-2% in developed countries. Males demonstrate slightly higher infection rates in pediatric populations but comparable rates in adults. Transmission occurs through direct contact with infected individuals or through autoinoculation from one body site to another. Shared sports equipment, pools, bath facilities, and close contact in childcare settings increase transmission risk. HIV-positive patients with CD4 less than 100 cells/microliter demonstrate dramatically elevated prevalence, with reports of 15-30% of such patients developing molluscum contagiosum. Molluscum contagiosum is reportable disease in some jurisdictions and is considered sexually transmitted infection when involving anogenital region. Recurrence after apparent complete resolution remains uncommon but documented in approximately 5-10% of cases.

Pathophysiology

Molluscum contagiosum virus (MCV) belongs to Poxviridae family and replicates exclusively in cytoplasm of host keratinocytes, unlike most DNA viruses that replicate in nucleus. The virus is large (approximately 300 nanometers), with double-stranded DNA genome approximately 190 kilobase pairs. MCV inoculation occurs through breaches in skin barrier or mucous membrane epithelium, followed by viral entry and cytoplasmic replication within keratinocytes. Productive viral infection induces characteristic cytopathic effects including formation of large cytoplasmic inclusions (molluscum bodies) filled with viral particles and host cell material. These inclusions become increasingly prominent as infection progresses, eventually filling the center of the lesion and comprising the umbilicated material that exudes when lesion ruptures. Viral proteins interfere with host immune response, including expression of proteins homologous to immune mediators including IL-18 binding protein and TNF receptor. The immune response to MCV involves both innate and adaptive immunity, with type 1 interferon responses and CD8+ T-cell responses critical for viral clearance. Lesion inflammatory response intensifies over time as immune response mounts, often culminating in inflammatory papule or pustule formation that signals viral clearance. Autoinoculation occurs through scratching or trauma, disseminating viral-laden material to other sites. Immunocompromised individuals develop extensive molluscum due to impaired T-cell mediated immunity critical for MCV control.

Clinical Presentation

Molluscum contagiosum typically presents as groups of pearly, dome-shaped, non-tender papules measuring 2-5 millimeters in diameter, though lesions can grow to 1 centimeter or larger with chronicity. The pathognomonic feature is central umbilication (dimple or indentation) visible on individual lesions. The surface is smooth and waxy in appearance, with fleshy or yellowish coloration. Lesions appear gradually over weeks, often in crops in anatomically contiguous areas due to autoinoculation from scratching. Common sites in children include face, trunk, and flexural areas including antecubital and popliteal fossae. In sexually active adults, lesions frequently localize to anogenital region, lower abdomen, and medial thighs. Perilesional dermatitis frequently develops as inflammatory response mounts, creating surrounding erythematous halo and pruritus. Pruritus ranging from mild to severe may accompany lesions, particularly in atopic individuals. Secondary bacterial infection can occur through scratching, creating pustular lesions. Rarely, giant molluscum forms develop as single large lesion (greater than 1 centimeter) representing unusual morphologic variant. Immunocompromised individuals develop more numerous lesions (sometimes hundreds), with less prominent umbilication and slower spontaneous resolution compared to immunocompetent hosts.

Diagnosis

Diagnosis of molluscum contagiosum is primarily clinical, based on characteristic pearly, dome-shaped, umbilicated papules. Dermoscopy enhances visualization of central umbilication and characteristic vascular patterns. Gram staining of expressed material demonstrates eosinophilic hyaline inclusion bodies (molluscum bodies) that are pathognomonic for the condition. Viral culture of MCV remains difficult as virus grows poorly in standard cell cultures. PCR testing of lesion material can identify MCV species (Type 1, 2, 3, or 4) with MCV-1 being most common. Histopathological examination demonstrates characteristic cytopathic effects including large cytoplasmic inclusions (molluscum bodies) within keratinocytes in central area of lesion, surrounded by inflammatory infiltrate with variable degree depending on lesion age. Direct immunofluorescence is not typically needed but can identify MCV antigen. Electron microscopy reveals characteristic brick-shaped viral particles of appropriate size to confirm poxvirus morphology. Differential diagnosis includes common warts (which lack central umbilication and have different vascular pattern), milia, and other papular dermatoses.

Treatment Algorithm

Multiple treatment options exist for molluscum contagiosum, with treatment decisions influenced by number of lesions, patient age and skin sensitivity, and potential for autoinoculation. Observation alone remains reasonable approach given self-limited nature and eventual spontaneous resolution in 6-24 months. Curettage or extraction of central core through direct mechanical removal represents effective treatment achieving 95%+ clearance in treated lesions, though autoinoculation must be prevented. The procedure involves using fine curette or needle to express the central molluscum body, followed by cautery or application of antimicrobial cream. Cryotherapy with liquid nitrogen applied via contact method achieves clearance in 50-80% of lesions, though multiple treatments separated by 2-4 weeks are required. Cryotherapy causes ice-crystal formation within cells triggering necrosis. Post-inflammatory erythema and occasional blistering represent expected effects. Topical imiquimod 5% cream applied under occlusion 5 nights per week for up to 16 weeks stimulates TLR7 signaling inducing T-cell responses against MCV. Efficacy rates of 60-75% reported, though prolonged treatment duration limits compliance. Topical tretinoin 0.025-0.05% applied nightly for 8-12 weeks induces inflammatory response and viral clearance in some patients. Salicylic acid 20-40% applied daily with mechanical paring facilitates clearance through maceration. Potassium hydroxide 10% solution applied directly to lesions three times daily causes chemical destruction, though irritation risk limits use. Cidofovir 1% cream topical application or injection has demonstrated efficacy in immunocompromised patients with extensive disease. Pulsed dye laser and other laser modalities have demonstrated efficacy but cost limits routine use.

Prognosis

Prognosis for molluscum contagiosum is excellent in immunocompetent individuals, with spontaneous resolution occurring in 90% of cases within 24 months. However, individual lesion persistence may extend 6-12 months even without treatment. Treated lesions demonstrate rapid clearance when appropriate method selected, with cure rates of 80-95% achievable with combination approaches. Recurrence after apparent complete resolution occurs in approximately 5-10% of cases. Post-inflammatory hyperpigmentation or hypopigmentation may persist temporarily but typically resolves. Immunocompromised patients demonstrate markedly different prognosis with extensive, persistent lesions requiring aggressive therapy. HIV-positive patients with CD4 count restoration through antiretroviral therapy often experience spontaneous molluscum resolution even without specific treatment. Rare complications include secondary bacterial infection creating pustular lesions and local cellulitis requiring systemic antibiotics.

When to See a Dermatologist

Patients with extensive molluscum contagiosum or immunocompromised status should seek dermatology consultation for treatment optimization. Children with facial involvement affecting appearance merit specialist evaluation. Those with secondary bacterial infection or failed initial treatment warrant specialist assessment. Adults with anogenital molluscum should receive evaluation to rule out other sexually transmitted infections.

Frequently Asked Questions

Q: Is molluscum contagiosum sexually transmitted?
A: Yes, molluscum can be transmitted through sexual contact, particularly when involving anogenital region. However, most cases in children result from non-sexual contact transmission.

Q: Will molluscum contagiosum go away on its own?
A: Yes, approximately 90% of cases resolve spontaneously within 24 months. However, some patients prefer treatment to accelerate resolution and prevent spread to contacts.

Q: Can I spread molluscum to others?
A: Yes, molluscum is highly contagious through direct contact and can spread through shared towels, clothing, or grooming implements. Avoiding direct contact and maintaining good hygiene reduces transmission risk.

Q: Is molluscum contagiosum dangerous?
A: No, molluscum is benign and typically resolves without complications in healthy individuals. Complications are rare and include secondary bacterial infection or significant post-inflammatory pigmentation changes.

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