What are diseases characterized by eschar and how are they managed?

Diseases Characterized by Eschar: Diagnosis and Management

Eschar formation is a key diagnostic feature in several infectious diseases, with anthrax and rickettsial infections being the most clinically significant conditions requiring prompt recognition and treatment to reduce mortality.

Major Diseases Presenting with Eschar

1. Cutaneous Anthrax

• Clinical presentation:

  • Initial painless, pruritic papule progressing to vesicle over 1-2 days
  • Development of characteristic black eschar with surrounding edema (often massive and disproportionate to lesion size)
  • Systemic symptoms may include fever, malaise, headache, and toxicity 1
  • Approximately one-third of patients develop fever 1

• Diagnosis:

  • Gram stain or Wright stain of lesion showing gram-positive bacilli
  • Culture from lesion or blood
  • PCR testing of lesion material
  • Serology for antibody detection

• Management:

  • First-line therapy: Ciprofloxacin (500 mg orally twice daily) or doxycycline (100 mg orally twice daily) for 60 days 1
  • For severe cases with systemic involvement, extensive edema, or head/neck lesions: IV therapy with multidrug regimen (ciprofloxacin + rifampin + clindamycin) 1
  • Consider corticosteroids for extensive edema, especially in head and neck region 1
  • Antimicrobial treatment may render lesions culture-negative within 24 hours, but progression to eschar still occurs 1

2. Rickettsial Diseases

• Clinical presentation:

  • Eschar present in approximately 33% of patients with scrub typhus 2
  • Sudden onset of fever, severe headache, malaise, and myalgias after 6-21 day incubation period
  • Maculopapular rash (may become petechial) typically appears 2-4 days after fever onset
  • Neurological manifestations in 18% of patients
  • Acute respiratory distress syndrome in 9% of patients 2

• Diagnosis:

  • Serology (IgM ELISA, indirect immunofluorescence)
  • PCR (particularly useful for eschar samples)
  • Immunohistochemistry of skin biopsies 2

• Management:

  • First-line therapy: Doxycycline for all ages, including children 2
    • Adults: 100 mg every 12 hours orally or IV
    • Children <45 kg: 2.2 mg/kg every 12 hours (maximum 100 mg per dose)
  • Treatment duration: 5-7 days or until 48-72 hours after patient is afebrile
  • Alternative: Azithromycin (especially for pregnant women) 2
  • Early treatment (within first 5 days) significantly reduces mortality 2

3. Mucormycosis (Cutaneous Form)

• Clinical presentation:

  • Common in immunocompetent patients after skin disruption (trauma, burns)
  • Abscesses, skin swelling, necrosis, dry ulcers, and eschars 1
  • May progress to invasive disease in immunocompromised patients

• Diagnosis:

  • Tissue biopsy with histopathology and culture
  • Direct microscopy showing broad, ribbon-like, aseptate hyphae

• Management:

  • Aggressive surgical debridement of necrotic tissue
  • Antifungal therapy (amphotericin B formulations)
  • Control of underlying conditions (especially diabetes)
  • Mortality rates range from 40-80% depending on site and host factors 1

4. Ecthyma Gangrenosum

• Clinical presentation:

  • Eschar-like skin ulcers typically caused by Pseudomonas aeruginosa
  • Common in immunocompromised patients
  • May mimic tropical diseases 3

• Management:

  • Appropriate antibiotics based on culture and sensitivity
  • Surgical debridement may be necessary
  • Combined approach with antibiotics, surgical intervention, and immunoglobulins for immunocompromised patients 3

Diagnostic Approach to Eschar

1. Detailed history:

   • Recent travel to endemic areas
   • Animal contact (especially livestock for anthrax)
   • Insect/tick bites (rickettsial diseases)
   • Immune status
   • Occupation (animal handlers, wool/hide workers at risk for anthrax)

2. Physical examination:

   • Characteristics of eschar (size, location, surrounding edema)
   • Associated rash
   • Systemic signs of infection
   • Lymphadenopathy

3. Laboratory testing:

   • Complete blood count
   • Blood cultures
   • Lesion sampling for Gram stain, culture, PCR
   • Serology for suspected pathogens

Treatment Principles

1. Early empiric therapy is crucial - don't wait for laboratory confirmation when clinical suspicion is high
2. Appropriate antimicrobial selection based on suspected pathogen
3. Surgical intervention when indicated (especially for mucormycosis)
4. Supportive care for systemic manifestations
5. Management of underlying conditions (especially immunosuppression, diabetes)

Prevention

• Vaccination for high-risk individuals (animal workers, military personnel) for anthrax 4
• Protective clothing and repellents in endemic areas for rickettsial diseases 2
• Prompt inspection and removal of ticks after outdoor activities 2
• Avoidance of contact with sick animals or their products (for anthrax) 5

Common Pitfalls

1. Delayed diagnosis due to failure to recognize eschar as a key diagnostic feature
2. Inadequate treatment duration - especially for anthrax, which requires prolonged therapy (60 days) 1
3. Monotherapy for severe infections - multidrug regimens are often required for severe anthrax
4. Failure to consider bioterrorism in unusual clusters of cases 1
5. Delayed surgical intervention for mucormycosis, which requires aggressive debridement

Early recognition of eschar-forming diseases and prompt initiation of appropriate therapy are essential to reduce morbidity and mortality, particularly for anthrax and rickettsial infections where early intervention significantly improves outcomes.