What is the appropriate diagnosis and treatment for a 7-year-old male presenting with fever and fluid-filled pustules for 3 days?

Approach to a 7-Year-Old Male with Fever and Fluid-Filled Pustules for 3 Days

This presentation requires immediate risk stratification to distinguish between benign drug-induced acute generalized exanthematous pustulosis (AGEP) versus life-threatening conditions like Rocky Mountain Spotted Fever (RMSF) or meningococcemia. 1, 2

Immediate Assessment: Red Flags for Life-Threatening Conditions

First, examine the rash morphology and distribution carefully:

• Petechial or purpuric rash pattern (not simple pustules) suggests RMSF or meningococcemia and demands immediate intervention 3, 1, 2
• Palm and sole involvement is pathognomonic for RMSF and requires immediate doxycycline 3, 1, 2
• True pustules on erythematous base without petechiae suggest AGEP or other drug reaction 4, 5, 6

Assess for systemic toxicity immediately:

• Altered mental status, hypotension, or respiratory distress indicate meningococcemia or severe RMSF 1, 2
• Progressive clinical deterioration over 3 days is a red flag for RMSF 3, 1
• RMSF has 50% mortality if deaths occur within 9 days of onset, with mortality increasing dramatically with each day of delayed treatment 1

Critical History Elements

Obtain these specific details immediately:

• Recent medication exposure (antibiotics are the most common cause of AGEP, particularly beta-lactams, clindamycin, and fluoroquinolones) 4, 5, 6
• Tick exposure or geographic risk (up to 40% of RMSF patients report no tick bite, so absence does not exclude diagnosis) 3, 1, 2
• Timing of rash relative to fever (AGEP typically occurs 7 days after drug exposure with fever and pustules appearing together; roseola shows rash after fever breaks) 1, 4, 5
• Outdoor activities, camping, or dog exposure in the past 2 weeks 3

Immediate Laboratory Workup

If any red flags are present, obtain before antibiotics:

• Complete blood count with differential (thrombocytopenia <150 x 10⁹/L suggests RMSF; leukocytosis >10,000/mm³ with neutrophilia suggests AGEP) 3, 1, 4, 7
• Comprehensive metabolic panel (elevated hepatic transaminases suggest RMSF) 3, 1
• C-reactive protein 1, 2
• Blood culture 3, 1, 2
• Acute serology for R. rickettsii if tick exposure possible or geographic risk present 3, 1

Treatment Algorithm

If Petechiae/Purpura OR Palm/Sole Involvement OR Systemic Toxicity:

Start doxycycline immediately (2.2 mg/kg orally twice daily), regardless of age, even in children <8 years 3, 1, 2

• Delay in recognition is the most important factor associated with death from RMSF 3, 1
• Mortality is 0% if treated by day 5, but 33-50% if delayed to days 6-9 1
• Also administer intramuscular ceftriaxone pending blood culture results, as meningococcal disease cannot be reliably distinguished from RMSF on clinical grounds alone 3, 2
• Immediate hospitalization required 1, 2

If Nonfollicular Sterile Pustules on Erythematous Base WITHOUT Red Flags:

This presentation is consistent with AGEP:

• Immediately discontinue any recently started medications (especially antibiotics started within the past 7-14 days) 4, 5, 6
• AGEP is characterized by hundreds of sterile pustules on erythematous, edematous skin with fever and leukocytosis 4, 5, 6
• Supportive care only: antipyretics (acetaminophen or ibuprofen) and hydration 1
• AGEP is self-limiting and resolves within 2 weeks after discontinuation of the offending agent 4
• No antibiotics are indicated for AGEP 4, 5

Disposition Decision

Immediate hospitalization if:

• Child appears toxic or has signs of sepsis 1, 2
• Petechiae, purpura, or progressive clinical deterioration 1, 2
• Palm/sole involvement 3, 1, 2
• Hypotension, altered mental status, or respiratory distress 1, 2

Outpatient management acceptable if:

• Well-appearing child with reassuring vital signs 1, 2
• No red flags present 1, 2
• Examination consistent with AGEP (nonfollicular pustules on erythema without petechiae) 4, 5
• Mandatory 24-hour follow-up, as serious infections are frequently missed at first presentation 2

Critical Pitfalls to Avoid

• Never delay doxycycline if RMSF is suspected based on patient age—the risk of death far outweighs theoretical dental staining risk 3, 1, 2
• Do not be falsely reassured by absence of tick bite history—40% of RMSF cases have no reported tick exposure 3, 1, 2
• Early serology is typically negative in the first week of RMSF, so do not wait for results before treating 3, 1
• Do not prescribe antibiotics for presumed AGEP—this worsens the condition and delays resolution 4, 5