A 7-month-old boy with a history of severe atopic dermatitis and asthma was brought for evaluation of a generalized rash, fever, and irritability of 2 days' duration. He had no respiratory symptoms. His medical history was significant for anorexia, without vomiting or diarrhea. He had a strong family history of allergy.
The ill-looking infant had a widespread, confluent, vesiculopustular rash with surrounding erythema, extensive scabbing, and crusting. Some umbilicated pustules were noted on the face and extremities. Flexor areas of the upper extremities showed some excoriation and fissures with areas of bleeding.
Further examination revealed hepatomegaly, with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels of 477 U/L and 202 U/L, respectively. An ultrasonogram of the abdomen showed hepatic parenchymal disease and mild to moderate left hydronephrosis. The infant was admitted to the hospital, and treatment with intravenous acyclovir, ceftriaxone, and vancomycin was started. By the third day of treatment, the AST and ALT levels dropped to 70 U/L and 106 U/L, respectively. No ocular involvement was noted. Polymerase chain reaction assay was positive for herpes simplex virus (HSV) type 1. Culture of fissures grew methicillin-resistant Staphylococcus aureus (MRSA).
This patient's presentation is characteristic of eczema herpeticum—infection of eczematous skin with HSV. Also known as Kaposi varicelliform eruption, eczema herpeticum is a dermatological emergency. Untreated infections may lead to complications, including herpes keratitis and disseminated HSV infection with visceral involvement. HSV1 is commonly implicated.
The rash begins as dome-shaped vesicles that later become punched-out excoriations, crusts, and erythematous plaques. The head, neck, and trunk are most commonly affected. Systemic symptoms, such as fever and malaise, usually accompany the rash. The rash recurs on chronic atopic lesions.
Patients with high total serum IgE levels and early age at onset of atopic dermatitis are more susceptible to eczema herpeticum. Risk factors include use of topical corticosteroids and topical calcineurin inhibitors.
The differential diagnosis includes erythema multiforme, varicella, impetigo, keratosis pilaris (with HSV infection), and pemphigus foliaceus (with HSV infection). In addition to testing for HSV infection, cultures to detect bacteria are helpful.
Antiviral agents (acyclovir, valacyclovir) remain the cornerstone of treatment. Acyclovir-resistant HSV infection is more common in immunocompromised children and responds to treatment with parenteral foscarnet. Topical antivirals may be necessary for treatment or prevention of keratoconjunctivitis. Antibiotic therapy may be needed for bacterial superinfection—as in this case.
At follow-up, the patient's treatment consisted of oral valacyclovir and clindamycin. He had no fever or hepatomegaly, and the rash had begun to resolve. Appropriate measures for skin care were reinforced.