A 10-month-old boy with an asymptomatic rash is brought to your office by his mother. The rash, which began on the legs and spread to the arms, face, and buttocks, has been present for 3 days. Other than rhinorrhea and nasal congestion for the past 3 to 5 days, the infant has been well, although fussier than usual, especially at night. His appetite is normal. The rash has persisted despite the application of bacitracin, petroleum jelly, and cortisone. He has had no sick contacts with a similar rash or illness. His immunizations are up-to-date.
One week earlier, a 14-month-old girl with a history of eczema was evaluated because of a diffuse rash of excoriated lesions, some of them purulent. She was afebrile. Worsening eczema with secondary infection was diagnosed. Treatment with oral clindamycin was prescribed. At follow-up, the lesions had worsened. The child had multiple excoriated papules, some of which had coalesced into plaques. She also had two 5-mm vesicles on her right shoulder. Eczema herpeticum was diagnosed clinically. Culture of the vesicles later grew herpes simplex virus (HSV).