FIGURE 68.6 A characteristic well-demarcated erythematous circular plaque with a dusky center seen with a fixed drug eruption (Reprinted with permission from Somolinos AL, Grant LM, Goldsmith LA, et al VisualDx: Essential Dermatology in Pigmented Skin Philadelphia, PA: Lippincott Williams & Wilkins; 2011.) FIGURE 68.7 This erythematous oval plaque occurred at the identical site where it occurred the last time this patient was exposed to a sulfonamide antibiotic (Reprinted with permission from Goodheart HP Goodheart’s Photoguide of Common Skin Disorders 2nd ed Philadelphia, PA: Lippincott Williams & Wilkins; 2003.) Erythema Multiforme The lesions of EM have a classic target appearance, which appears as a welldefined round macule or papule with three distinct zones: two concentric rings around a dusky, bullous, or crusted center ( Fig 68.8A,B ) The lesions are symmetrically distributed and favor the distal extremities, especially the upper extremities Mucous membrane lesions can be seen in up to half of cases Bullous lesions rupture easily, leaving swelling and crusting ( Fig 68.9 ) EM lesions are fixed, with individual lesions lasting approximately days Systemic symptoms of malaise, low-grade fever, myalgias, or arthralgias may be present EM is a hypersensitivity reaction most often secondary to an infectious trigger EM has been associated with many infectious agents, including bacterial, viral, fungal, and parasitic infections Herpes simplex virus and and Mycoplasma are the most common infectious triggers Medications may be a cause of EM, most commonly sulfonamides, antiepileptic medications, and antibiotics FIGURE 68.8 A, B: Classic target lesions seen in erythema multiforme with three distinct zones (A: Reproduced with permission from Roche Laboratories Sauer GC, Hall JC Manual of Skin Diseases 7th ed Philadelphia, PA: Lippincott-Raven, 1996 B: Reprinted with permission from Somolinos AL, Grant LM, Goldsmith LA, et al VisualDx: Essential Dermatology in Pigmented Skin Philadelphia, PA: Lippincott Williams & Wilkins, 2011.) EM is often confused for urticaria or SJS EM can be distinguished from the transient and pruritic lesions of urticaria because of the classic target appearance of lesions that are fixed for several days As discussed further below, SJS is a severe drug eruption that has lesions that are often confused for the targetoid lesions of EM, but they lack the characteristic three zones Furthermore, in SJS, two or more mucous membranes are typically involved with blisters, erosions, and crusting EM is a self-limited reaction resolving within to weeks Because of its frequent association with herpes simplex virus, patients are often treated with acyclovir If a medication trigger is suspected, then stopping the medication will help with resolution Antihistamines can offer symptomatic relief FIGURE 68.9 Erosions on the lips with target lesions on the hands (Reprinted with permission from Somolinos AL, Grant LM, Goldsmith LA, et al VisualDx: Essential Dermatology in Pigmented Skin Philadelphia, PA: Lippincott Williams & Wilkins; 2011.) Stevens–Johnson Syndrome/Toxic Epidermal Necrolysis SJS and toxic epidermal necrolysis (TEN) are clinically similar, but exist in a spectrum distinguished by the degree of skin involvement SJS involves 30% of body surface area; and 10% to 30% body surface area involvement is considered SJS/TEN overlap A prodrome of fever and constitutional symptoms (malaise, headache, sore throat, myalgias, arthralgias) sometimes precedes the onset of cutaneous lesions Erythematous and purpuric macules start on the face and trunk and spread over hours to a few days to become more confluent and bullous Tender erosions remain after the bullae rupture ( Fig 68.10 ) As the erythematous macules develop dusky centers indicating epidermal necrosis, they can have a targetoid appearance but lack the classic three zones seen in the target lesions of EM Gentle lateral pressure to an area of macular erythema causes the epidermis to sheer off, known as the Nikolsky sign Postinflammatory dyspigmentation is common Mucous membrane involvement can precede cutaneous involvement by to days Two or more mucosal surfaces are usually involved, while any epithelial