A female infant delivered at term by cesarean section had a “blueberry muffin” rash at birth. On physical examination, multiple purple, papulonodular lesions measuring 5 to 10 mm in diameter were seen on her trunk, arms and legs, palms and soles, oral mucosa, and palpebral conjunctiva. There was no lymphadenopathy or hepatosplenomegaly, and the results of funduscopy were normal.
The results of initial laboratory tests, including a complete blood count, a peripheral-blood smear, a reticulocyte count, a metabolic panel, and a coagulation test, were normal. A chest radiograph was normal, as were the results of ultrasonography of the head and abdomen. Neither rubella nor cytomegalovirus IgM or IgG was detected in the mother or the infant.
What is the diagnosis ?