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Within this chapter, we will explore a group of diseases in which the diagnosis and management (or triage), are a key task for clinicians in a variety of scenarios. The patients affected by these disorders span from infants to elders, and from healthy to immunosuppressed. Prompt recognition and therapeutic intervention are crucial for these disorders, in order to prevent or mitigate the significant potential morbidity (and in some cases, mortality). These conditions share mucocutaneous blistering or desquamation, and may demonstrate, especially early in course, overlapping clinical features with non-emergent exanthems; thus, particular attention will be paid to the historical and examination findings which best help distinguish these disorders from each other and from non-urgent diagnoses.



Key points for erythema multiforme (EM)

  • ✓ EM is an acute, self-limited, but sometimes recurrent immune-mediated mucocutaneous eruption.

  • ✓ About 90% of cases are caused by upper respiratory infections, and most commonly by herpes simplex virus (HSV-1).

  • ✓ EM presents with target like pink lesions on the face, palms, extremities and trunk. Vesicles and erosions may be present on oral mucus membranes. Systemic symptoms are minimal.

  • ✓ Most patients do not require treatment, but patients with significant oral involvement may need supportive care for pain and hydration.

Experts once believed that erythema multiforme (EM), Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) were all one disease on a spectrum of severity, with EM the mildest form and TEN the most severe. More recently, however, efforts to link disease morphology with their cause have led to reconsideration; most experts now believe that EM and SJS/ TEN are separate diseases with distinct pathophysiology. Erythema multiforme (EM) is an acute, self-limited, but sometimes recurrent immune-mediated mucocutaneous eruption.1,2 It presents most commonly as targetoid skin lesions in young adults and may include findings of mucositis and/or skin blistering. Many affected patients have a history of herpes simplex virus (HSV) infection or demonstrate HSV seropositivity.


There remains considerable debate about what causes erythema multiforme; infections, medications, malignancies, autoimmune disease, immunizations, radiation, sarcoidosis, menstruation, and other causes have been implicated.1 Most experts believe that up to 90% of cases of EM are caused by infections, with herpes simplex virus (HSV) the most commonly implicated agent.1–4 In addition to HSV, a wide range of bacterial, viral, fungal, and parasitic infections have also been implicated (Table 18-1). Some believe that drugs are an uncommon cause of EM, while others believe that they are a common cause and are involved in up to half of cases.1 While many drugs have been implicated, the most common culprit drugs identified are also those also most commonly implicated in SJS/TEN: antibiotics (especially sulfa and penicillins), anticonvulsants, and non-steroidal anti-inflammatory drugs. Experts who believe that EM is an ...

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