Visual Diagnosis

Presentation

A 28-day-old, previously healthy, full-term girl presents to the emergency department after 2 days of irritability and 1 day of a rash. She has had no fevers, hypothermia, cough, congestion, increased work of breathing, easy bleeding or bruising, jaundice, or other symptoms. She was born via a scheduled repeat cesarean delivery at 38 weeks’ gestation after an uncomplicated pregnancy. Her mother received adequate prenatal care and had no serologic evidence of prenatal infections. After 3 days in the well-infant nursery, the child was discharged. No one at home is currently ill; however, the patient’s 8-year-old sister had a “cold sore” ∼2 weeks before admission.

On approximately day 10 after birth, the patient’s mother had an outbreak of painful “itchy blisters” that started on her lower back, then spread to the inguinal region and abdomen, appearing most prominently over her cesarean delivery scar. She does not remember whether the rash was unilateral or bilateral. The lesions have scabbed over and resolved. The mother has never had a similar rash in the past and denies a history of herpes or other sexually transmitted infections. Both parents had chickenpox during childhood. The older siblings have been fully immunized. Family history is unremarkable for any immunodeficiencies or inherited childhood diseases.

Physical examination reveals an afebrile, somewhat fussy but consolable girl infant. Vital signs are all within normal range. Skin findings reveal ∼20 vesicles with an erythematous base that are scattered over the face (Fig 1), trunk, legs, plantar surfaces (Fig 2), and buttock. The patient has normal work of breathing, no hepatosplenomegaly, and no mucous membrane involvement. The remainder of her physical examination is …