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Erythema Multiforme, Stevens-Johnson Syndrome, and Toxic Epidermal Necrolysis
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A 14-year-old boy presents to the emergency department with a 1-day history of fever associated with lip swelling and peeling (Figure 185-1A). Within 48 hours he developed involvement of his ocular (Figure 185-1B) and urethral mucosa along with an erythematous papular rash on his trunk that spread to his extremities. In Figure 185-1C, target lesions can be seen on his back. He was diagnosed with Stevens-Johnson syndrome and admitted to the hospital.
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Erythema multiforme (EM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) are skin disorders thought to be types of hypersensitivity reactions (undesirable reactions produced by a normal immune system in a presensitized host) that occur in response to medication, infection, or illness. Both SJS and TEN are severe cutaneous reactions thought to describe the same disorder, differing only in severity (TEN more severe); however, there is debate as to whether these three fall into a spectrum of disease that includes EM.
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EM has also been called EM minor.
SJS has been called EM major in the past but is now thought to be a distinct entity different from all types of EM.
TEN is also known as Lyell syndrome.
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The incidence of EM has been estimated to range from 1 in 1000 persons to 1 in 10,000 persons.1 The true incidence is unknown.1
SJS and TEN are rare severe cutaneous reactions often caused by drugs. Reports of incidence vary from 1.2 to 6 per 1 million for SJS and from 0.4 to 1.2 per 1 million for TEN.2-4
EM is rare in children under age 3 years and adults over age 50 years: 20% of cases occur in children and adolescents.5
With respect to EM, males are affected more often than females (3:2 to 2:1).5
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ETIOLOGY AND PATHOPHYSIOLOGY
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Numerous factors have been identified as causative agents for EM:
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Herpes simplex virus (HSV) I and HSV II are the most common causative agents, having been implicated in at least 60% of cases (Figure 185-2).6,7 The virus has been found in circulating blood,8 as well as on skin biopsy of patients with EM minor.6
Bacterial causes are numerous and ...