What is the initial approach to treating a patient with Erythema multiforme (EM)?

Initial Approach to Treating Erythema Multiforme (EM)

The initial approach to treating erythema multiforme should focus on identifying and removing the triggering cause, providing symptomatic relief with topical corticosteroids, and implementing appropriate supportive care based on disease severity.

Etiology Identification and Management

• First step is to identify and address the underlying cause:

  • Herpes simplex virus (HSV) - most common infectious trigger 1
  • Mycoplasma pneumoniae infection 1, 2
  • Medication reactions - particularly NSAIDs and other drugs 2

• Immediately discontinue any suspected causative medications 2

Treatment Algorithm Based on Severity

Mild EM (Limited Cutaneous Involvement)

1. Topical corticosteroids - First-line therapy for cutaneous lesions 3, 4

   • Apply high-potency topical corticosteroids to affected areas 2-3 times daily
   • FDA-approved for severe erythema multiforme 3

2. Symptomatic relief:

   • Oral antihistamines for pruritus 1
   • Topical lidocaine 2-4% for painful lesions 2

Moderate to Severe EM (Extensive Cutaneous or Mucosal Involvement)

1. Systemic corticosteroids - Consider for severe cases 3, 4

   • Prednisone 40-60 mg daily for 5-7 days with taper 5
   • Most effective when started early in the disease course

2. Antiviral therapy - For HSV-associated EM 5

   • Acyclovir 400 mg three times daily for 7-10 days

3. Mucosal care:

   • Oral: Aluminum/magnesium hydroxide mouthwash for comfort 2
   • Ocular: Urgent ophthalmology consultation to prevent long-term sequelae 2
   • Genital: Topical lidocaine for pain relief 2

Recurrent EM

1. Antiviral prophylaxis - First-line for HSV-associated recurrent EM 1, 5

   • Acyclovir 400 mg twice daily
   • Valacyclovir 500 mg daily

2. Second-line options for refractory cases 4:

   • Immunosuppressive agents
   • Antimalarials
   • Antibiotics for Mycoplasma-associated EM

Important Distinctions and Pitfalls

• Distinguish EM from Stevens-Johnson Syndrome (SJS) 6:

  • EM: Typically acral distribution with target lesions, limited mucosal involvement
  • SJS: Widespread erythematous/purpuric macules with blisters, extensive mucosal involvement
  • Biopsy may help in unclear cases (subepidermal cleavage in SJS/TEN) 6

• Avoid misdiagnosis with erythromelalgia 6, 7:

  • Erythromelalgia presents with burning pain and redness in extremities
  • Treated differently with aspirin as first-line therapy 7

Monitoring and Follow-up

• Monitor for progression to more severe disease
• Assess for ocular complications which may require specialized care 2
• Evaluate for recurrence, especially with HSV-associated EM

Prognosis

• Most cases of EM are self-limited and resolve within 2-3 weeks 1
• Mortality is lower in children compared to adults 6
• Long-term sequelae are more common with mucosal involvement, particularly ocular complications 2

By following this structured approach to EM management, clinicians can effectively treat the condition while minimizing complications and preventing recurrence.