Erythema Multiforme

EM minor & EM with mucosal involvement

• Self-limited, recurrent disease, usually in young adults

• No or only a mild prodrome (1 to 4 weeks)• Sharply marginated erythematous macules

become raised, edematous papules (24 to 48 hours)• Periphery: ring of erythema

Central: flatters, more pruritic and dusky

Classic EM lesion• “target” or “iris” lesion with three zones

• Best observed on the palms and soles• Symmetrical and acral

1. Central dusky purpura2. Elevated, edematous,

pale ring3. Surrounding macular

erythema

Sites of Predilection• Dorsal feet• Extensor limbs• Elbows• Knees• Palms • Soles

• Koebner’s phenomenon or photoaccentuation• Mucosal involvement in 25%

-- usually limited to the oral mucosa• More severe classic case? Two or more

mucous membranes involved in 45%

Steven-Johnson syndrome / EM major

• Clinically different from minor• Frequently, febrile prodrome• Eruption occurs at all ages• Begins diffusely on the truck and mucous

membranes• Flat, erythematous or purpuric macules

incomplete “atypical targets” (may blister centrally)• Larger and more commonly confluent lesions

compared to EM minor

Etiologic Factors • EM minor = herpes simplex infection– Typically orolabial– 1 to 3 weeks (10 day average) after herpes lesion– May or not follow herpes outbreaks

• EM major (SJS) = medications– Most centrally accentuated eruptions with atypical

targets – Sulfonamids, antibiotics, NSAIDs, allopurinol,

anticonvulsants– Due to abnormal metabolism of medications

Etiologic Factors

• Also, EM major = Mycoplasma pneumoniae– Prominent mucosal involvement and bullous skin

lesions – NOT classic iris lesions– Resemble SJS cases

• And, EM major = radiation therapy– With phenytoin and tapering corticosteroids –

induces EM starting at radiation port

Pathogenesis

• Activated T lymphocytes – Epidermis: cytotoxic or suppressor cells – Dermis: helper T cells

• EM minor – specific HLA types (HLA-DQ3)• SJS – abnormalities in drug metabolism

Hence, there is a genetic component for both diseases

HistopathologyHistopathological findings Immunofluorescence findings

Apoptosis of individual keratinocytes Granular deposits of IgM and C3 around superficial blood vessels

spongiosis Focal granular deposits of IgM and C3 at the dermal-epidermal junction

Focal vacuolar degeneration of basal keratinocytes

Superficial dermal edema

Perivascular infiltrate of mononuclear leukocytes

T lymphocytes with exocytosis into the epidermis

Apoptosis of keratinocytes

Spongiosis

Focal vacuolar degeneration of basal keratinocytes

Differential Diagnosis

• Herpes simplex• Drug eruptions• Giant urticaria• Stevens-Johnson syndrome• Dermatitis herpetiformis

Treatment

Type of Erythema Multiforme Management

EM Minor •Symptomatic treatment- antihistamines, analgesics (3 to 4 days)•Topical steroids

EM Major •Symptomatic treatment- antihistamines, analgesics (3 to 4 days)•Burow solution dressing for severe skin lesions•Xylocaine and Diphenhydramine elixir for oral ulcers•Antibiotics if secondary infection is suspected•Oral Acyclovir (10 mg/kg/day in divided doses)•Systemic steroids- Prednisone (0.5 – 1 mg/kg/day)