What is the best course of action for a 2-year-old male toddler with a history of eczema (atopic dermatitis) and a delayed vaccination schedule, presenting with diarrhea, low-grade fever, dysuria, irritability, fatigue, and a progressive morbilliform rash?

Immediate Evaluation for Eczema Vaccinatum from Contact Transmission

This child requires urgent evaluation for eczema vaccinatum (EV), a potentially life-threatening complication that occurs when vaccinia virus from a recently vaccinated contact spreads to a person with atopic dermatitis, and if confirmed, immediate treatment with vaccinia immune globulin (VIG) is imperative to reduce mortality from 30-40% to 7%. 1

Critical First Steps

Obtain Vaccination Exposure History

• Ask specifically if any household members, daycare contacts, or close contacts received smallpox vaccination within the past 5-19 days, as this is the typical timeframe for EV to develop after secondary transmission 1
• The delayed vaccination schedule makes this child particularly vulnerable, as unvaccinated contacts of vaccinees experience more severe EV than vaccinees themselves 1
• Even if parents deny eczema history in contacts, proceed with EV evaluation, as two-thirds of potential vaccinees fail to recall exclusionary dermatologic conditions 1

Examine the Rash Characteristics

• Look for vesicular or pustular lesions that follow the same dermatological course (Jennerian progression) as a vaccination site, with predilection for areas of previous eczema involvement 1
• Confluent or erosive lesions strongly suggest EV rather than other viral exanthems 1
• The progressive nature of this morbilliform rash combined with systemic illness (fever, irritability, fatigue) is highly concerning for EV 1

Differential Diagnosis Considerations

Rule Out Other Serious Conditions

• Eczema herpeticum from herpes simplex virus presents similarly but typically has known sick contacts with cold sores; obtain PCR from vesicular fluid to distinguish 2, 3
• Generalized vaccinia (GV) occurs in immunocompetent hosts but patients appear well, not systemically ill like this child 1
• The diarrhea and dysuria suggest systemic involvement beyond simple viral gastroenteritis, consistent with the systemic illness seen in EV 1

Immediate Management Algorithm

If EV is Suspected Based on Exposure History and Rash Pattern

1. Admit immediately for intensive monitoring and supportive care 1

• EV patients require hemodynamic support similar to sepsis management 1
• Meticulous skin care as for burn victims is essential 1
• Volume repletion and vigilant electrolyte monitoring are necessary due to disruption of the dermal barrier 1

2. Obtain diagnostic confirmation while initiating treatment 1

• Collect vesicular fluid for vaccinia virus PCR and viral culture
• Do not delay VIG administration while awaiting results, as early treatment is imperative to reducing mortality 1

3. Administer VIG immediately 1

• Multiple doses may be required for severe cases 1
• This is the single most important intervention that reduced EV mortality from 30-40% to 7% 1

4. Implement strict infection control precautions 1

• Virus can be isolated from EV lesions, making these patients highly infectious 1
• Contact precautions prevent secondary transmission and nosocomial infection 1

5. Monitor for secondary bacterial and fungal infections 1

• Administer antibacterials and antifungals as necessary 1
• Obtain cultures of affected lesions to guide therapy 3

If No Vaccination Exposure Can Be Identified

Consider alternative diagnoses but maintain high suspicion for EV 1

• Evaluate for eczema herpeticum with HSV PCR testing 2, 3
• Assess for other causes of vesicular rash with systemic illness
• The dysuria may indicate urinary tract infection requiring separate evaluation with urinalysis and culture

Critical Pitfalls to Avoid

• Never delay VIG treatment while awaiting diagnostic confirmation if clinical presentation and exposure history suggest EV 1
• Do not dismiss the possibility of EV based on negative parental recall of contact eczema, as screening is notoriously unreliable 1
• Recognize that this child's history of eczema places them at highest risk for EV regardless of current disease activity 1
• Understand that contact-acquired EV tends to be more severe than EV in vaccinees, possibly due to simultaneous multiple inoculations 1

Prognosis and Long-term Considerations

• With early VIG administration and aggressive supportive care, survival is expected in >90% of cases 1
• Recovery may require prolonged hospitalization (up to 48 days documented) with burn-type management including possible skin grafts 4
• Most children recover without significant systemic sequelae if treated promptly 4