Erythema Multiforme - just the facts

Erythema Multiforme - just the facts

ETIOLOGY

- Herpes Simplex Virus Infection (Labialis and Genitalis)

- most common ; 60%

PATHOGENESIS

- "unclear"

- probably - Host-specific cell-mediated immune responses to an antigenic stimulus

- result: Keratinocyte damage

CLINICAL MANIFESTATION

- Classic lesion: Doughnut-shaped, target-like (iris or bull's eye) Papules

- with Erythematous outer border ;  Inner pale ring ; dusky purple to necrotic center

- most commonly on the extensor upper extremities 

- lesions are relatively sparse on the face, trunk, and legs

- oral lesions may occur with a predilection for the vermilion border of the lips and the buccal mucosa

DIFFERENTIAL DIAGNOSIS

• Bullous pemphigoid
• Pemphigus
• Linear IgA dermatosis
• Graft versus Host Disease
• Bullous drug eruption
• Urticaria
• Viral Infection (Herpes Simplex)
• Reiter disease
• Behcet disease
• Allergic vasculitis
• Erythema annulare centrifugum
• Kawasaki disease
• Periarteritis Nodosa

Involvement of oral mucosa:

• Bullous pemphigoid
• Pemphigus vulgaris
• Vesiculobullous or erosive lichen planus
• Behçet syndrome
• Recurrent aphthous stomatitis
• Primary herpetic gingivostomatitis

MICROSCOPIC CHARACTERISTIC (Organ Affected)

1. Early Lesions

• slight intercellular edema
• rare dyskeratotic keratinocytes
• basal vacuolation in the epidermis
• perivascular lymphohistiocytic infiltrate with edema in the upper dermis

2. Mature Lesions

• early lesions +
• lymphocytic exocytosis
• intense, perivascular, and interstitial mononuclear infiltrate in the upper third of the dermis

3. Severe Cases

• entire epidermis becomes necrotic

MANAGEMENT

1. Supportive

• Topical emollients
• Systemic Anti-Histamines
• NSAIDs

2. Prophylactic

• Oral ACYCLOVIR for 6 months (to control recurrent episodes of HSV-associated EM)

Reference: Nelson Textbook Of Pediatrics 18th Edition