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Table 17.1 describes the names and descriptions of primary dermatological lesions.
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An immune-mediated self-limited rash most commonly triggered by herpes simplex virus infection. Rash without mucosal involvement is termed erythema multiforme (EM) minor while that with mucosal involvement, EM major. It is now considered to be distinct from and not on a continuum with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Additional triggers include other viral, bacterial or fungal infection and medications.
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Erythematous, papular rash (Figure 17.1) appears over 72 hours, most commonly on palms and dorsal surface of forearms but also on feet, face, and lower extremities, usually < 10% BSA. There is great variation, but typically > 100 lesions are present.
Papules may evolve to target lesions with a characteristic central dusky or purple zone surrounded by a pale ring and then third erythematous halo.
Lesions may have a vesicular or bullous appearance.
Discrete oral lesions are present in approximately 50% of patients.
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Stevens-Johnson syndrome/toxic epidermal necrolysis: Skin and oral lesions are more severe and progress to skin necrosis and sloughing.
Urticaria: Lesions migrate (EM lesions are fixed, persists > 24 hours).
See Table 17.2 for differential diagnosis of rashes on the palms.
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