A 3-year-old boy presents to the emergency department (ED) with a 1-day history of irritability and listlessness. According to his parents, he was well until the night before when he began to behave abnormally, becoming excessively tired approximately 2 hours after eating dinner. During the night, the boy slept poorly, sporadically awakening with crying followed by brief periods of calmness. The morning of presentation, he was difficult to arouse with intermittent fussiness and reluctance to ambulate.
