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 purpura 2.Elevated, edematous, pale ring 3.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

Histopathology Histopathological findingsImmunofluorescence findings Apoptosis of individual keratinocytesGranular deposits of IgM and C3 around superficial blood vessels spongiosisFocal 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 MultiformeManagement 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)