Erythema Multiforme (EM)
Epidemiology:
Common sites:
Gross features:
- symmetric
involvement of the extremities frequently
- multiform lesions
- macules
- papules
- vesicles
- bullae
- characteristic
target lesion
- red macule or papule with a pale, vesicular, or eroded
centre
- Stevens-Johnson
syndrome:
- Erosions and
hemorrhagic crusts involving lips and oral mucosa
- conjunctiva,
urethra, genital, and perianal areas may be
involved
- toxic epidermal necrolysis (TEN):
- diffuse necrosis
and sloughing of cutaneous and mucosal
epithelial surfaces
Histologic features:
- prototypical cytotoxic reaction pattern
- early:
- superficial perivascular, lymphocytic
infiltrate
- dermal edema
- interface
dermatitis
- accumulation of
lymphocytes along dermoepidermal junction
- intimately
associated with degenerating and necrotic keratinocytes
- basal cell vacuolation
- CD8+ cytotoxic T cells kill the epithelial cells
- later:
- upward migration
of lymphocytes into epidermis
- discrete and
confluent zones of epidermal necrosis with blister formation and
erosions
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- hypersensitivity
reaction to certain infections and drugs
- infections:
- herpes
simplex
- mycoplasmal infections
- histoplasmosis
- coccidioidomycosis
- typhoid
- leprosy
- others
- drugs:
- sulfonamides
- penicillin
- barbiturates
- salicylates
- hydantoins
- antimalarials
- malignancies:
- collagen
vascular diseases:
- lupus
erythematosus
- dermatomyositis
- periarteritis nodosa
- Stevens-Johnson
syndrome is an extensive and symptomatic febrile form:
- Often
children
- May
have superinfection and sepsis
- Toxic epidermal necrolysis is another variant
References: