Case Presentation: A 19-year old female with history of atopic dermatitis and herpes simplex virus (HSV) labialis presented with a 3 day complaint of facial rash. The rash was preceded by two days of sore throat, fever, and body aches. She was initially evaluated at an urgent care clinic where she was prescribed cephalexin for a presumed upper airway infection. Two days prior to admission, she returned to urgent care with persistent symptoms and was prescribed azithromycin and oral steroids. Symptoms persisted and the patient presented to the Emergency Department. She denied vision changes, new sexual partners, or recent travel. Physical examination was significant for fever of 101.7°F, tachycardia to 144 beats per minute and for erythematous xerotic plaques over the forehead, cheeks, nose, chin, and bilateral antebubital fossae with punched out ulcerations and significant yellow crusting. Four mucosal ulcerations were noted on the soft palate of the mouth. Eczema herpeticum (EH) was suspected, and intravenous acyclovir was initiated plus vancomycin for presumed superimposed bacterial infection. Both viral culture and direct immunofluorescence assays of the lesions were positive for HSV-1, and a superficial wound culture grew methicillin-susceptible Staphylococcus aureus. After all lesions crusted over, she was discharged on oral valacyclovir and cephalexin to complete a total of 14 days.

Discussion: EH, also known as Kaposi varicelliform eruption, refers to disseminated HSV infection in the context of atopic dermatitis. This is a frequently missed entity and most commonly observed in the pediatric population. Despite the high prevalence of both HSV infection and of atopic dermatitis, EH is very rare. It occurs in less than 3% of patients with atopic dermatitis. The pathophysiology of this disease involves an epidermal barrier breakdown of the stratum corneum which then serves as a fertile ground for the lateral dissemination of active HSV infection. EH is a medical emergency and presents as dome-shaped vesicular clusters in areas of chronic eczematous dermatitis. The diagnosis can be made by Tzanck smear of vesicular fluid, direct fluorescent antibody staining of the vesicular fluid, or viral culture. Patients with EH are at a high-risk of secondary impetigo and bacteremia necessitating topical/systemic antibiotics. Antivirals are the mainstay for therapy; use of topical glucocorticoids is controversial. The mortality rate can be up to 9% without proper management. Most deaths are due to viremia-induced multi-organ failure, including meningitis and encephalitis. Given the high potential mortality, EH should always be considered in the differential diagnosis when a new rash appears in patients with chronic atopic dermatitis.

Conclusions: EH is a rare but potentially life-threatening viral infection. Internists, including medicine trainees, should be aware of its presentation and the need for prompt and appropriate therapy to avoid potential complications.