What is the likely cause of recurring fluid-filled bumps on the chin in a pediatric patient?

Recurring Fluid-Filled Bumps on the Chin in Children

The most likely diagnosis is molluscum contagiosum, a self-limited viral infection presenting as flesh-colored, waxy papules with central umbilication that wax and wane over months, and the recommended management is observation with spontaneous resolution expected within 6-12 months. 1

Clinical Presentation and Diagnosis

Molluscum contagiosum presents as discrete, flesh-colored to waxy papules measuring 2-5 mm in diameter with characteristic central umbilication (the "fluid-filled" appearance parents describe). 1 The lesions:

• Express white, cheesy sebaceous material when compressed (molluscum bodies) 1
• Typically affect the trunk, face (including chin), and extremities in children 1
• Are usually asymptomatic without pain, pruritus, or erythema in uncomplicated cases 1
• Affect 5-11% of children aged 0-16 years 1

Diagnosis is primarily clinical based on the characteristic appearance of umbilicated papules. 1 Histologic examination or PCR can be performed in complex or unclear cases, though this is rarely necessary. 1

Pathophysiology of Recurrence Pattern

The infection is caused by molluscum contagiosum virus (MCV), a poxvirus transmitted through direct skin-to-skin contact or fomites. 1 The "comes and goes" pattern parents describe reflects:

• New lesions appearing as the virus spreads to adjacent skin
• Individual lesions resolving spontaneously while new ones develop
• The natural waxing and waning course over 6-12 months (though complete resolution can take up to 4 years) 1

Recommended Management Approach

Expectant observation is the gold standard approach, with resolution occurring spontaneously in 6-12 months in most cases. 1 No treatment is required for asymptomatic lesions. 1

When to Consider Active Treatment

Active treatment may be considered for:

• Cosmetic concerns
• Lesions in areas prone to autoinoculation
• Immunocompromised patients
• Parental preference after counseling

Treatment modalities with similar efficacy include: 1

• Cryotherapy with liquid nitrogen - commonly used but may cause postinflammatory hyperpigmentation or scarring 1
• 10% potassium hydroxide - efficacy similar to cryotherapy 1
• Cantharidin - effective therapy with high parental satisfaction rates, though evidence is limited to open-label studies 1

Imiquimod is not shown to be beneficial compared to placebo in randomized controlled trials. 1

Activity Restrictions

For athletes and children in organized sports or swimming, guidelines recommend: 1

• Covering lesions to avoid skin-to-skin contact
• Not sharing towels and fomites
• Limiting exposure to swimming pools during active outbreaks

Important Differential Diagnoses to Exclude

While molluscum is most likely, consider these alternatives based on specific features:

Neonatal or infantile acne (if age <6 months to 7 years): 2, 3

• Presents with comedones, papules, pustules rather than umbilicated papules
• More common in males (4.5:1 ratio) 2
• Typically involves forehead, cheeks, chin 2

Viral warts (verruca vulgaris): 4

• Lack central umbilication
• Have rough, hyperkeratotic surface
• May require surgical excision if on face to prevent spread 4

Impetigo (if lesions are truly fluid-filled bullae): 4

• Honey-crusted appearance when ruptured
• Requires topical mupirocin 2% or oral antibiotics 4

Critical Pitfalls to Avoid

• Do not confuse with serious blistering disorders - Stevens-Johnson syndrome presents with widespread purpuric macules, blisters, and mucosal involvement requiring immediate specialized care 4
• Avoid unnecessary aggressive treatment - spontaneous resolution is the norm and aggressive treatment may cause scarring 1
• Do not restrict normal activities unnecessarily - simple covering of lesions allows participation in most activities 1