Skin-nontumor / Clinical Dermatology

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Skin-nontumor / Clinical Dermatology

Blistering disorders

Erythema multiforme

Reviewer: Mowafak Hamodat, MB.CH.B, MSc., FRCPC (see Reviewers page)
Revised: 26 August 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

General
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● Acute, self limited, hypersensitivity reaction to infections (coccidioidomycosis, herpes simplex, histoplasmosis, leprosy, mycoplasma, typhoid), drugs (penicillin, phenylbutazone, phenytoin, salicylates, sulfa), carcinoma / lymphoma, or collagen vascular disorders
● Affects skin (distal extremities, palms, soles) and mucous membranes with target lesions
● Also sore throat and malaise
● Any age
● Commonly recurs, but rarely persists

Clinical images
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● Variable (multiform) lesions – papules, macules, vesicles, bullae, target lesions
● Commonly in mucous membranes; also elbows, knees, extensor surface of extremities

Clinical images
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Target Lesions

Micro description
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● Subepidermal bullae with basement membrane in bullae roof due to dermal edema
● Severe dermal inflammatory infiltrate (includes lymphocytes, histiocytes)
● Eosinophils may be present, but neutrophils are sparse or absent
● Overlying epidermis often demonstrates liquefactive necrosis and degeneration, dyskeratotic keratinocytes
● May also have dermoepidermal bullae with basal lamina at floor of bullae
● Variable epidermal spongiosis and eosinophils
● No leukocytoclasis, no microabscesses, no festooning of dermal papillae
● Note: erythema multiforme may have variable histologic changes from toxic epidermal necrolysis to dermal disturbances

Micro images
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Various images

Virtual slides
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Erythema multiforme

Positive stains
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● Granular C3 and IgM at basement membrane and in vessels

Differential diagnosis
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● Acute graft versus host disease: clinical history; early changes are basal layer vacuolization and necrosis, spongiosis, apoptosis, acantholysis, chronic inflammation of upper dermis with perivascular lymphocytic infiltrate and intraepidermal lymphocytes
● Fixed drug reaction: eosinophils and marked vascular wall thickening
● Steven Johnson syndrome or toxic epidermal necrolysis: full thickness epidermal necrosis with separation of epidermis from dermis; necrotic keratinocytes at edge of bullae
● Subacute cutaneous lupus erythematosus: fibrinoid necrosis at dermoepidermal junction with liquefactive degeneration and atrophy of epidermis

Additional references
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● eMedicine

End of Skin-nontumor / Clinical Dermatology > Blistering disorders > Erythema multiforme

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