Erythema Multiforme Clinical Presentation
I cannot provide actual images, but I can describe the characteristic clinical appearance of erythema multiforme in detail to help you recognize it.
Pathognomonic Skin Lesions
The hallmark of erythema multiforme is the presence of typical "target" or "iris" lesions that are raised, symmetrically distributed, and start on acral (extremity) surfaces before progressing proximally 1, 2.
Target Lesion Characteristics:
- Three distinct zones creating a bull's-eye appearance:
- Central dark red or dusky area (may blister or become necrotic)
- Pale edematous middle ring
- Outer erythematous ring
- Raised and palpable (unlike flat macules in Stevens-Johnson syndrome)
- Fixed in location for minimum of 7 days (distinguishes from urticaria which resolves within 24 hours) 3
- Diameter typically 1-3 cm
Distribution Pattern
Lesions characteristically begin on the dorsal hands, palms, extensor surfaces of forearms and legs, then spread centrally toward the trunk 2, 3. The distribution is:
- Symmetrical
- Acral predominance (hands, feet, elbows, knees)
- Extensor surfaces favored over flexor surfaces
Mucosal Involvement
In erythema multiforme major (EMM), mucosal erosions and ulcerations occur, most commonly affecting the oral cavity, particularly the labial mucosa (86.1% of cases) 4. The mucosal lesions present as:
- Painful erosions and ulcerations
- Hemorrhagic crusting of lips
- Usually confined to the mouth (unlike SJS/TEN which involves multiple mucosal sites) 1
Key Distinguishing Features from Stevens-Johnson Syndrome
Erythema multiforme is clinically distinct from SJS/TEN 1:
- EM has raised target lesions; SJS has flat atypical targets or purpuric macules
- EM starts acrally and spreads centrally; SJS starts on trunk
- EM patients are constitutionally well; SJS patients appear systemically ill
- EM has limited mucosal involvement (usually just oral); SJS has extensive mucosal involvement
- EM does not progress to widespread epidermal detachment
Clinical Context
The typical patient presents with 2, 3:
- Recent herpes simplex virus infection (most common trigger) or Mycoplasma pneumoniae
- Acute onset of characteristic target lesions over 24-48 hours
- Mild constitutional symptoms or none
- Good overall appearance despite dramatic skin findings
This clinical picture, when combined with the characteristic targetoid morphology and acral distribution, makes erythema multiforme readily recognizable without requiring imaging studies.