What is the diagnosis and treatment for a 7-year-old female with a painful, flesh-colored bump on her upper arm, which has worsened after attempted popping and has a possible family history of molluscum contagiosum?

Diagnosis: Inflamed Molluscum Contagiosum

This is an inflamed molluscum contagiosum lesion that requires active treatment given the pain, worsening after manipulation, and risk of transmission to siblings who already have molluscum. 1, 2

Clinical Reasoning

The presentation is classic for molluscum contagiosum with inflammation:

• Flesh-colored, dome-shaped papule with possible central lighter area (umbilication) is pathognomonic for molluscum 1, 2
• Two siblings with confirmed molluscum on their neck establishes household transmission and confirms the diagnosis 2, 3
• Pain and burning after attempted manipulation indicates secondary inflammation, which commonly occurs when molluscum lesions are traumatized 2
• Worsening after attempted "popping" is expected—trauma to molluscum lesions causes local inflammatory response without resolution since the viral material remains in the dermis 2, 4

The lighter central area without an opening represents the characteristic umbilication of molluscum, which may be subtle in inflamed lesions 1, 2. The burning sensation and pain distinguish this from typical asymptomatic molluscum and indicate the lesion has become irritated 2.

Treatment Approach

For this single, painful, inflamed lesion, physical destruction via cryotherapy with liquid nitrogen is the treatment of choice 4:

• Cryotherapy is preferred for symptomatic, inflamed lesions as it provides immediate destruction and prevents further autoinoculation 3, 4
• Apply liquid nitrogen for 10-20 seconds until a 1-2mm halo of freeze extends beyond the lesion margin 3
• Single treatment session is often sufficient for isolated lesions 4

Alternative Treatment Options (in order of preference):

• Curettage: Scrape out the central core with a curette after topical anesthetic; provides immediate resolution but requires local anesthesia in children 3, 4
• Cantharidin 0.7-0.9%: Apply to lesion, wash off in 2-6 hours; causes blistering that destroys the lesion within 24-48 hours 3, 4

What NOT to Do:

• Do not attempt further manual expression or "popping"—this worsens inflammation, causes pain, and spreads viral particles to surrounding skin 2
• Watchful waiting is inappropriate here given the symptomatic nature, inflammation, and household transmission risk 2, 3

Prevention of Household Transmission

Implement these measures immediately to prevent spread to other body sites and family members 2, 5:

• Avoid sharing towels, clothing, or bathing together until all lesions resolve 2
• Cover the lesion with waterproof bandage until treated to prevent autoinoculation and transmission 2
• Examine all siblings weekly for new lesions on neck and other areas 2
• Treat new lesions promptly when they appear to limit spread 3, 4

Expected Course

• Treated lesions typically resolve within 1-2 weeks after cryotherapy 4
• Mild hypopigmentation may occur at treatment site but usually resolves over months 2
• Monitor for new lesions over the next 6-9 months, as the incubation period can be 2-6 weeks and autoinoculation is common 2, 5