A 27-year-old woman comes to the emergency department with a 1-day history of skin rash. Two weeks ago, she had an episode of recurrent genital lesions, which began with small papules and subsequently became vesicular with ulceration, crusting, and eventual healing. The patient has no other medical conditions and takes no medications. On physical examination, she appears comfortable. Temperature is 37 C (98.6 F). She has small linear erosions in the oral mucosa. Skin findings are shown in the image below. Which of the following is the most likely diagnosis?

Question

A 27-year-old woman comes to the emergency department with a 1-day history of skin rash.  Two weeks ago, she had an episode of recurrent genital lesions, which began with small papules and subsequently became vesicular with ulceration, crusting, and eventual healing.  The patient has no other medical conditions and takes no medications.  On physical examination, she appears comfortable.  Temperature is 37 C (98.6 F).  She has small linear erosions in the oral mucosa.  Skin findings are shown in the image below.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

This patient's rash is consistent with erythema multiforme (EM), an acute inflammatory disorder that can involve the skin of the extremities, face, trunk, and neck. Severe cases (EM major) can also affect oral mucous membranes and the tongue. The appearance of EM can vary, but patients typically develop erythematous, round papules that evolve into target lesions with a dusky central area, a dark red inflammatory zone surrounded by a pale ring, and an erythematous halo in the lesion's periphery. EM represents a cell-mediated immune process, with an inflammatory infiltrate predominated by cytotoxic CD8⁺ lymphocytes. EM is most frequently associated with infections (especially herpes simplex virus and mycoplasma) and may be due to an immune response against antigens deposited in the skin. EM can also be seen in association with certain medications (eg, sulfonamides), malignancy, and collagen vascular diseases. (Choice A) Disseminated herpes simplex infection is seen primarily in immunocompromised patients and presents with diffuse vesicles on an erythematous base. EM does not represent disseminated infection, but is a systemic immune response to a localized infection. (Choice C) Primary HIV infection can present with a macular or maculopapular rash associated with fever. The rash is usually well circumscribed and involves the trunk, face, and palms and soles. However, this patient's rash appears more typical of EM. (Choice D) Stevens-Johnson syndrome is characterized by rapid onset of erythematous macules with necrosis and skin sloughing. Systemic signs (eg, fever, hypotension) are common. Stevens-Johnson syndrome may also cause target lesions, but it is usually associated with medications (eg, sulfonamides, allopurinol, phenytoin). (Choice E) Varicella typically presents with fever and a vesicular eruption that can affect multiple areas, including the face, trunk, abdomen, and extremities. This patient's rash does not have the typical vesicular pattern seen in varicella. Educational objective: Erythema multiforme is a cell-mediated inflammatory disorder of the skin characterized by erythematous papules that evolve into target lesions. It is most commonly associated with herpes simplex virus. __________ References: Erythema multiforme: a review of epidemiology, pathogenesis, clinical features, and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/24034067) Clinical features, diagnosis, and treatment of erythema multiforme: a review for the practicing dermatologist. (http://www.ncbi.nlm.nih.gov/pubmed/22788803)

A 27-Year-Old Woman Comes to the Emergency Department with a 1-Day