Chapter 164 Erythema Multiforme
Diagnostic Summary
• Sudden onset of symmetrical erythematous, edematous, macular, papular, urticarial, bullous, or purpuric skin lesions
• Evolves into “target lesions” (lesions with clear centers and concentric erythematous rings)
• Characteristic first site: dorsum of the hand
• Characteristic distribution: extensor surfaces of extremities with relative sparing of head and trunk
• Although rare, oral manifestations ranging from tender superficial erythematous and hyperkeratotic plaques to painful, deep, hemorrhagic bullae and erosions
General Considerations
The term erythema multiforme (EM) includes a wide range of clinical expressions, from exclusive oral erosions (oral EM) to mucocutaneous lesions ranging from mild (EM minor) to severe involvement of multiple mucosal membranes (EM major, Stevens-Johnson syndrome [SJS]) or with involvement of a large area of the total body surface (toxic epidermal necrolysis [TEN]). However, this terminology is not accepted worldwide, and often the various clinical categories show some overlapping features. Although significant differences exist among EM minor, EM major, SJS, and TEN with regard to severity and clinical expression, all variants share two common features: typical or less typical cutaneous target lesions and satellite-cell or more widespread necrosis of the epithelium. Clinically, EM major is characterized by typical or raised atypical targets located on the extremities and/or face. SJS is diagnosed when lesions are flat, atypical targets or purpuric maculae that are widespread or distributed on the trunk.1
