Erythema exudativum multiforme. Erythema nodosum.
Erythema exudativum multiforme is an acute self-limited inflammation reaction with a typical target or iris lesions; hypersensitivity reaction usually triggered by infections, medications and other various triggers. It may be present within a wide spectrum of severity:
- a) EM minor
- b) EM major (more severe)
- Epidemiology: young adults (20-40 yrs) with male dominance.
- Pathogenesis: The vast bulk of recurrent cases are triggered by Herpes simplex Virus (HSV) infection. Other triggers include mycoplasma and rarely drugs.
- Clinical features: target lesions are usually found on the distal extremities, mouth and genitalia.
- Erythema multiforme minor - Typical targets or raised, edematous papules distributed acrally. prodromal symptoms are usually absent or mild. The abrupt onset of a rash usually occurs within 3 days, starting on the extremities symmetrically, with centripetal spreading. Pruritus is generally absent.
- Erythema multiforme major - Typical targets or raised, edematous papules distributed acrally with involvement of one or more mucous membranes; epidermal detachment involves less than 10% of total body surface area (TBSA). Patients have prodromes similar to an influenza like prodrome, including moderate fever, general discomfort, cough, sore throat, vomiting, chest pain, and diarrhea. symptoms have a classic time course of development and are usually present for 1-14 days before the cutaneous eruption occurs. The lesions begin on the acral areas and spread similarly to the distribution of erythema multiforme minor.
- Steven-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are considered severity variants of a single entity. Clinically appear as widespread blisters predominant on the trunk and face, presenting with erythematous or pruritic macules and one or more mucous membrane erosions; epidermal detachment is less than 10% TBSA for Steven-Johnson syndrome / toxic epidermal necrolysis and 30% or more for toxic epidermal necrolysis.
- Histology: necrotic keratinocytes, vascular degeneratium in basal layer, papillary dermal edema with lymphocytic perivascular infiltrates.
- Diagnosis: Skin biopsy; History of HSV or Drug exposure. Cultures are indicated in severe cases and should be obtained from blood, sputum, and mucosal lesions. No specific imaging studies are necessary in most cases, although chest radiography may be useful in cases with respiratory symptoms or signs, particularly if an underlying pulmonary infection is suspected.
- Treatment: Systemic corticosteroids (prednisone (60-80 mg x 3-5 days); anti-hepatic medication.