An asymptomatic lesion with positive Darier sign on an infant

A healthy 12-month-old infant girl presents with a yellowish-orange papule on the right upper extremity. Her mother first noticed this lesion approximately 6 months earlier. It has never bled, ulcerated, or formed blisters. The infant does not scratch the lesion nor appears otherwise bothered by it. However, when the lesion is rubbed, it appears to swell and turn bright red. ...