The patient’s presentation reveals a dependent vesicular purpuric rash with necrosis. The next step in treatment is to obtain the patient’s sexual history. The patient confirmed having unprotected sexual intercourse with a new partner approximately 2 to 3 weeks before the onset of the rash. The rash has not been accompanied by any genital symptoms (currently or in the interim). Because of suspicion for EM, a herpes serology was ordered, and herpes simplex virus type 2 immunoglobulin M testing was found to be positive.

EM is a dermatologic condition characterized by pink painful target lesions and patches that may evolve to bullae, which eventually scab over. Lesions tend to start distally and may itch, but as the rash progresses, they become more painful than pruritic. The lesions typically last 1 to 4 weeks, which is the usual length of most viral illnesses. EM is differentiated from other rashes by the following characteristics: distal location, pain, target lesions, and bullae.

Causes of EM are mostly viral infections, mycoplasma infections, and certain medications. The most common cause of EM is herpes simplex virus; other causes include Epstein-Barr virus, hepatitis C, cytomegalovirus, and HIV. Treatment of EM involves a combination of treating the triggering infection, removing any triggering medications, and introducing antihistamines for symptomatic relief.

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Brady Pregerson, MD, is an emergency physician at Cedars-Sinai Medical Center in Los Angeles and at Tri-City Medical Center in Oceanside, California.


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