A 30-month-old boy is brought to the pediatric clinic by his parents due to concerns regarding his speech and social development. His parents report that he has a vocabulary of only three to four single words and does not put words together. He rarely makes eye contact, does not respond to his name when called, and does not point to objects to share interest. He frequently flaps his hands when excited and insists on lining up his toy cars in a specific order, becoming highly distressed if they are moved. His birth history and past medical history are unremarkable. He is not currently taking any medications.

He appears healthy and is playing independently in the corner of the room. His temperature is 98.6°F, blood pressure is 90/60 mmHg, heart rate is 100 beats per minute, and respiratory rate is 22 breaths per minute.