A full-term, healthy female newborn was delivered via cesarean section because the labor did not adequately progress. The mother, age 33 years and of Asian ancestry, had a significant medical and obstetrical history: chronic hepatitis B carrier without cirrhosis, cutaneous lupus erythematosus (positive anti-Ro and anti-La antibodies), and a positive group B streptococcal recto-vaginal culture at 35 weeks’ gestation. The mother received 4 doses of intravenous ampicillin during labor.
The infant’s initial hospital course was complicated by a transient and otherwise asymptomatic bradycardia. An electrocardiogram (ECG) confirmed a heart rate of 96 with normal interval parameters, but there were changes suggestive of left ventricular hypertrophy. An echocardiogram was normal.
Follow-up office visits for common newborn feeding problems demonstrated consistent weight gain and normal vital signs, including heart rate and facial milia. However, by age 4 weeks an erythematous eruption extending from the frontal scalp and forehead to the cheek area had developed (FIGURES 1 AND 2).
FIGURE 1
Rash on a newborn’s face …
FIGURE 2
…and on the scalp
What is the differential diagnosis?
What tests should be done to make the diagnosis?