What are the recommended diagnostic and treatment options for molluscum contagiosum?

Molluscum Contagiosum: Diagnosis and Treatment

Diagnosis

Molluscum contagiosum is diagnosed clinically by identifying characteristic dome-shaped, skin-colored to pink papules with central umbilication and a shiny surface, typically distributed on the trunk, face, and extremities in children. 1

Key Diagnostic Features

• Classic presentation: Discrete papules (2-5mm) with central umbilication containing a waxy core 1
• Early lesions may lack umbilication and appear as simple dome-shaped papules, requiring careful examination for shiny surface characteristics 1
• Distribution patterns: Trunk, face, and extremities in children; genital and perineal regions in sexually active adults 1, 2
• Associated findings: Perilesional eczema, conjunctivitis if near eyelids, or inflammatory reactions 1

Differential Diagnosis Considerations

When distinguishing from herpes simplex, look for stable papules over weeks to months (molluscum) versus grouped vesicles on erythematous base that rapidly progress to ulcers within 10 days (herpes). 3

• Herpes follows predictable rapid progression: erythema → papules → vesicles → ulcers → crusts in <10 days 3
• Molluscum lesions remain stable for weeks to months without spontaneous ulceration 3
• For any genital ulcerative or vesicular lesions, obtain laboratory confirmation with viral culture or NAAT, as clinical diagnosis alone is unreliable 3

Red Flags Requiring Further Evaluation

• Multiple large lesions with minimal inflammation suggest immunocompromised state and warrant HIV screening 1
• In immunocompromised patients, atypical presentations (giant, necrotic, polypoidal forms) may occur, and cryptococcal infection must be excluded 1

---

Treatment Algorithm

Step 1: Determine Need for Active Treatment

Physical removal (curettage, excision, or cryotherapy) is first-line therapy for symptomatic lesions, multiple lesions, or periocular lesions causing conjunctivitis. 1, 4

Active treatment is indicated when:

• Lesions are symptomatic (painful, pruritic, inflamed) 1
• Multiple lesions present (increased transmission risk) 1
• Periocular location with associated conjunctivitis 1, 4
• Patient desires treatment to prevent transmission or autoinoculation 4

Watchful waiting is reasonable for:

• Asymptomatic lesions 4
• Limited number of lesions 4
• No periocular involvement 4
• Spontaneous resolution typically occurs in 6-12 months (range: 6 months to 5 years) 1, 4

Step 2: Select Treatment Modality

First-Line Physical Removal Methods 1, 4

• Cryotherapy with liquid nitrogen: 93% complete response rate, but carries risk of postinflammatory hyperpigmentation (especially in darker skin) and uncommon scarring 1, 4
• Curettage, simple excision, or excision with cautery: Immediate removal with similar efficacy 1, 4
• Avoid treating sensitive areas (eyelids, lips, nose, ears) with cryotherapy due to higher complication risk 1

First-Line Chemical Treatment 1, 4

• 10% potassium hydroxide solution: Similar efficacy to cryotherapy (86.6% complete response) with better cosmetic results due to lower hyperpigmentation risk 1, 4
• Preferred for facial lesions or patients with darker skin tones 1

Alternative Chemical Treatment 1

• Cantharidin: Effective in observational studies with 86% parent satisfaction and no serious adverse events in 405 children over 1,056 visits 1
• Creates controlled blistering that destroys infected epithelium 1

Step 3: Treatment Execution Principles

Identify and treat ALL lesions, including nascent ones, during the initial treatment session to reduce recurrence risk. 1

• Examine carefully for early lesions that may appear as simple papules without umbilication 1
• Reducing viral load allows host immune response to eliminate residual virus 1
• Treatment success depends heavily on operator skill and complete application 1

Step 4: Special Populations and Situations

Periocular Lesions with Conjunctivitis 1, 4

• Physical removal is mandatory to resolve conjunctivitis 1, 4
• Conjunctivitis may require several weeks to resolve after lesion removal 1
• Monitor for conjunctivitis resolution at follow-up 1

Immunocompromised Patients 1

• Screen for immunodeficiency if extensive disease with minimal inflammation 1
• Consider dermatology referral for examination of suspicious lesions 1
• Chronic ulcerated lesions may develop secondary bacterial and fungal superinfections requiring culture-directed therapy 1

Pediatric Considerations 4

• Salicylic acid is contraindicated in children under 2 years due to systemic toxicity risk 4
• No anesthesia is typically used for cryotherapy, as it has not shown benefit 1

---

Treatments to AVOID

Imiquimod showed no benefit compared to placebo in randomized controlled trials and should not be used. 1, 4

• H2 blockers (ranitidine) have no evidence supporting efficacy and are not recommended 4

---

Prevention and Transmission Control

Hand hygiene with alcohol-based disinfectant or soap and water is the most important prevention method. 4

Specific Prevention Measures 4

• Avoid direct skin-to-skin contact with infected individuals 4
• Do not share towels, clothing, equipment, or personal items 4
• Cover all lesions with waterproof bandages if water exposure is unavoidable 4
• Limit exposure to swimming pools associated with known outbreaks 1
• Avoid scratching lesions to prevent autoinoculation 1
• Return to communal water activities only when all lesions have completely resolved and no new lesions have appeared for several weeks 1

---

Follow-Up and Monitoring

• Follow-up is not usually necessary unless conjunctivitis persists after periocular lesion removal 1
• Monitor for resolution of conjunctivitis over several weeks if periocular lesions were treated 1
• If extensive or recalcitrant disease, consider immunodeficiency screening 1

---

Critical Pitfalls to Avoid

• Do not miss nascent lesions during initial treatment—this is the most common cause of recurrence 1
• Do not neglect periocular lesions, as they require active treatment to prevent ocular complications 1
• Do not assume genital papules are molluscum without laboratory confirmation, as HSV is the most common cause of sexually acquired genital ulceration 3
• Do not diagnose bacterial superinfection based on erythema alone—this often represents normal inflammatory response as the immune system clears the virus 1
• True bacterial superinfection requires purulent drainage, marked cellulitis, or systemic signs; obtain culture confirmation before antibiotics 1