Erythema multiforme

Background

Erythema Multiforme

• Erythema Multiforme (EM) is an acute, self-limited skin condition precipitated by a variety of factors:
  • Infections:
    • Viral: HSV, hepatitis, influenza A
    • Fungal: dermatophytosis, histoplasmosis, coccidioidomycosis
    • Bacterial: streptococcus, tuberculosis
  • Drugs:
    • Antibiotics (penicillin, sulfonamides), anticonvulsants (phenytoin, barbiturates), NSAIDS, aspirin, antituberculous meds, allopurinol, etc.
  • Collagen Vascular Disorders:
    • RA, SLE, dermatomyositis, polyarteritis nodosa
  • Others:
    • Pregnancy, cold weather, sunlight, contact exposure, foods, malignancy, hormonal
• Peak incidence in second and third decades of life
• Despite multiple associations, thought to be triggered by HSV in most cases
• Usually self-limited and resolves within 2-6 weeks; may recur
• Wide spectrum of severity
  • Classified as Erythema multiforme minor or Erythema multiforme major

Clinical Features

• Erythematous or violaceous macules, papules, vesicles, or bullae
• Target lesions with “three zones of color” are the hallmark of EM
• Distribution is usually symmetric, most commonly involving palms/soles, the backs of the hands/feet, and/or the extensor surfaces of the extremities
• Not to be confused with SJS/TEN, which are now considered separate from the EM spectrum

1. Erythema multiforme minor
   1. Typical targets or raised, edematous papules distributed peripherally
   2. No mucous membrane involvement
2. Erythema multiforme major
   1. Same as EM minor + involvement of 1+ mucous membranes
   2. Epidermal detachment involves < 10% of total body surface area
   3. Some cases can be severe or even fatal

Differential Diagnosis

• Fixed drug reaction
• Steven-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN)
• Subacute cutaneous lupus erythematosus
• Urticaria
• Viral exanthems
• Allergic or irritant contact dermatitis