Erythema Multiforme Minor

 Erythema Multiforme - Minor

·         A self-limited but frequently recurrent disease

·         Abrupt onset of papular lesions with the vast majority of lesions appearing within 24 hours

·         Target lesions with central zone of damage: crusting, blisters or erosion and outer red zone

·         Target lesions may appear in sites of prior skin injury

·         Predominant precipitant is preceding herpes simplex virus infections (HSV)

·         Large urticarial lesions are frequently misdiagnosed as erythema multiforme

·         Erythema multiforme is a clinical not a histologic diagnosis

Erythema multiforme is an acute, self-limited skin disease characterized by the abrupt onset of symmetrical fixed red papules, some of which evolve into target lesions.  A target lesion consists of concentric zones of color change with evidence of damage to the epidermis in the central zone such as bulla formation or crust.  Early target lesions will have a central dusky zone and a red outer zone, but may evolve to three zones of color change. 

Epidemiology

Observed in young adults and very uncommon in childhood.  There is a slight male preponderance but no racial bias.

Pathogenesis

Precipitating factors:

  1. HSV
  2. ORF
  3. Histoplasm capsulatum
  4. Epstein-Barr

Majority of children and adults with EM is precipitated by HSV types I and II.  Preceding herpes labialis is noted in approximately 50% of subject with EM.  The herpes labialis may precede the onset of the cutaneous lesions, occur simultaneously or be evident after the target lesions of EM have appeared.

    • Herpes labialis precedes target lesions of EM by 3-14 days. 
    • Presumed most cases in kids and young adults are due to HSV type I, but cases of HSV type II have been reported
    • Inflammation within the cutaneous lesions is believed to be part of HSV specific host response