Four-year-old Richard is referred by his parents for evaluation. They report his birth had been difficult and he had needed oxygen after delivery. His physical appearance, motor development, and self help skills are all age appropriate, but his parents are concerned at his apparent lack of response to social contact and typical baby games.

Richard appears to be self sufficient but is aloof from others. He does not greet his mother in the mornings or his father when he comes home from work. He has no interest in other children and ignores his younger brother. His early babbling had no conversational intonation, but at age three he could clearly understand simple practical instructions. His speech consists of echoing words and phrases he has heard in the past, usually exactly mimicking the speaker's original tone and inflection. Doing this he can indicate some of his basic needs; for example, he will say "Do you want a drink?" to indicate that he is thirsty. He does not communicate using facial expression or gesture, except for pulling someone along and placing his or her hand on an object he wants.

Richard is captivated by bright lights and spinning objects, staring at them while laughing, flapping his hands and bouncing on tiptoe. He responds the same way to music, which he's enjoyed since very early in life. He is intensely attached to a miniature car, which he carries with him day and night, although he never plays imaginatively with it. He can very rapidly assemble jigsaw puzzles (using only one hand, with the car in the other), with the picture side up or down.

Richard has an intense resistance to any attempt to change his routine or expand his interests. Such attempts are typically met with protracted tantrums characterized by screaming, kicking, and biting of himself and others. His parents once feared he had hearing problems, but his love of music, his accurate echoing and his sensitivity to some very soft sounds convinced them that this was not the case. In intelligence testing Richard scored at the mental age of a three year old, but performed at the level of an 18 month old in terms of language comprehension.

What is the diagnosis and treatment?