Is erythema multiforme (EM) different from Stevens-Johnson syndrome (SJS)?

Erythema Multiforme and Stevens-Johnson Syndrome Are Distinct Clinical Entities

Yes, erythema multiforme (EM) and Stevens-Johnson syndrome (SJS) are different disorders with distinct clinical presentations, etiologies, and management approaches.

Key Differences Between EM and SJS

Clinical Presentation

• Erythema Multiforme:

  • Characterized by typical target lesions that start on acral surfaces (extremities) and progress proximally 1
  • Mucosal involvement (when present) is usually confined to the mouth 1
  • Patients are typically constitutionally well 1
  • Rarely leads to long-term complications 1

• Stevens-Johnson Syndrome:

  • Part of a spectrum with Toxic Epidermal Necrolysis (TEN) 1
  • Characterized by atypical flat targets or purpuric macules that are widespread or distributed on the trunk 1
  • Extensive mucosal involvement (eyes, mouth, nose, genitalia) is an early feature 1
  • Accompanied by systemic symptoms and constitutional disturbance 1
  • Can lead to significant long-term sequelae and has appreciable mortality 1

Etiology

• Erythema Multiforme:

  • Primarily triggered by infections, especially herpes simplex virus and Mycoplasma pneumoniae 1, 2
  • Rarely drug-induced 3

• Stevens-Johnson Syndrome:

  • Predominantly triggered by drugs 1
  • Rarely caused by infections (except for Mycoplasma pneumoniae in some pediatric cases) 1

Histopathology

• Erythema Multiforme:

  • Predominantly inflammatory pattern 4
  • Lichenoid infiltrate 4
  • Epidermal necrosis mainly affecting the basal layer 4

• Stevens-Johnson Syndrome:

  • Predominantly necrotic pattern 4
  • Major epidermal necrosis 4
  • Minimal inflammatory infiltration 4
  • Subepidermal vesicle or bulla formation 1

Severity and Prognosis

• Erythema Multiforme:

  • Self-limited condition 5
  • Good recovery with minimal sequelae 1

• Stevens-Johnson Syndrome:

  • Potentially life-threatening condition 1
  • Mortality rates vary: <10% for SJS, up to 30% for TEN 1
  • Significant long-term sequelae in survivors (particularly ophthalmic, mucocutaneous, and psychological) 1

Management Approaches

Erythema Multiforme

• Supportive treatment is generally considered sufficient 2
• For recurrent herpes-associated EM, prophylactic acyclovir may be beneficial 5
• When herpes-triggered, combination of acyclovir and prednisone during exacerbations 5

Stevens-Johnson Syndrome/TEN

• Requires immediate specialist care and often intensive care management 1
• Immediate discontinuation of any potential culprit drug 1
• Transfer to specialized centers with experience in managing SJS/TEN 1
• Multidisciplinary team approach including ophthalmology 1
• Supportive care with attention to fluid balance, wound care, pain management, and prevention of infection 1
• Immunomodulatory therapy may be considered (cyclosporine has shown promise) 2
• SCORTEN can be used to assess disease prognosis 2

Common Pitfalls in Diagnosis

1. Misclassification: Historically, EM with mucosal involvement was often incorrectly classified as SJS, leading to confusion in the literature 1, 3

2. Overlapping features: The presence of mucosal involvement in both conditions can lead to diagnostic confusion 3

3. Failure to recognize early SJS: Cutaneous pain is a prominent early feature in SJS/TEN and should alert physicians to incipient epidermal necrolysis 1

4. Inadequate assessment of lesion morphology and distribution: The key to differentiation is careful examination of:

   • Lesion type (typical targets in EM vs. atypical targets/purpuric macules in SJS)
   • Distribution pattern (acral/extremities in EM vs. trunk/widespread in SJS) 3

5. Overlooking the importance of biopsy: In cases of diagnostic uncertainty, histopathology can help differentiate between these conditions 4

The distinction between these conditions is crucial as it impacts management decisions, prognosis discussions, and follow-up care planning.