What are the causes and treatment options for vacciniforme scars, particularly in individuals with a history of smallpox vaccination or other skin conditions such as eczema or psoriasis?

Causes of Vacciniforme Scars

Primary Cause: Smallpox Vaccination

Vacciniforme scars are primarily caused by successful smallpox (vaccinia) vaccination, where the characteristic pitted, depressed scar forms as the normal endpoint of the vaccination process when the pustule dries and the scab separates 14-21 days after vaccination. 1

The normal vaccination progression involves:

• Papule formation at 3-5 days post-vaccination 1
• Vesicular stage at days 5-8 1
• Pustular enlargement reaching maximum size at 8-10 days 1
• Central drying with scab formation 1
• Scab separation at 14-21 days, leaving the characteristic pitted scar 1

This scar formation is actually a marker of successful "vaccine take" and historically correlated with immunity to smallpox. 1, 2

Secondary Cause: Hydroa Vacciniforme

Hydroa vacciniforme (HV) is a rare photodermatosis that produces smallpox-like scars but is unrelated to actual vaccination. 3

Key features of HV include:

• Rare childhood blistering photodermatosis associated with latent Epstein-Barr virus (EBV) infection 3
• Heals with depressed circinate scars resembling smallpox vaccination scars 3
• Typically presents in childhood and spontaneously resolves by early adulthood 3, 4
• Destruction of adnexal structures accounts for the characteristic depressed scars 3
• Rarely can present in adults (case reported at age 58) 4

Pathologic Vaccination Complications That Cause Extensive Scarring

Eczema Vaccinatum (EV)

Persons with atopic dermatitis (eczema) are at highest risk for developing eczema vaccinatum, which can cause extensive scarring due to widespread skin destruction. 1

Critical features:

• Occurs in individuals with history of atopic dermatitis, regardless of disease severity or activity 1
• Can result from direct vaccination or secondary transmission from vaccinated contacts 1
• Lesions follow Jennerian progression with confluent or erosive lesions 1
• Accompanied by fever, lymphadenopathy, and systemic illness 1
• Early diagnosis and administration of vaccinia immune globulin (VIG) reduces mortality from 30-40% to 7% 1
• Severe cases may require burn-unit level care with skin grafts 5

Common pitfall: Two-thirds of potential vaccinees fail to recall exclusionary dermatologic conditions like atopic dermatitis in themselves or close contacts, making screening challenging. 1

Progressive Vaccinia (PV)

Progressive vaccinia causes severe necrotic scarring when the vaccination site fails to heal and vaccinia virus replication persists, typically in immunocompromised individuals. 1

Characteristics:

• Rare, severe, and often fatal 1
• Skin surrounding vaccination site becomes infected with secondary metastatic lesions 1
• Lesions appear necrotic, fungated, piled-up, or well-demarcated 1
• Occurs in persons with humoral or cellular immune deficits 1
• Requires aggressive therapy with VIG or cidofovir, intensive monitoring, and tertiary-level supportive care 1

Fetal Vaccinia

Smallpox vaccination during pregnancy can rarely cause fetal vaccinia, resulting in pox-scarred infants if they survive. 1

Features include:

• Transmission occurs through presumed viremia at any time during pregnancy 1
• Can result in abortion, stillbirth, premature birth followed by death, or surviving pox-scarred infant 1
• Fetal/newborn skin lesions described as macular, papular, vesicular, pustular, or as scars or areas of epidermolysis 1

Keloid Formation

Individuals with darker skin and familial tendency can develop extensive keloid scars at vaccination sites, which may progress with additional vaccines given at the same sites. 6

Management considerations:

• Keloids extend beyond original wound boundaries 6
• Develop in anatomic areas exposed to increased skin tension 6
• Treatment is difficult but includes surgical excision, cryotherapy, radiation, and intralesional/topical corticosteroids 6

Clinical Algorithm for Evaluation

When encountering vacciniforme-appearing scars:

1. Obtain vaccination history: Confirm smallpox vaccination (most common cause in vaccinated individuals) 1

2. Assess for photodermatosis: If no vaccination history, consider hydroa vacciniforme, especially with childhood onset and sun-exposed distribution 3

3. Screen for atopic dermatitis: History of eczema dramatically increases risk of severe scarring from eczema vaccinatum 1

4. Evaluate immune status: Immunocompromised individuals risk progressive vaccinia with extensive necrotic scarring 1

5. Examine scar characteristics: Pitted scars suggest normal vaccination take; extensive, confluent scarring suggests pathologic complication 1, 5