A four-year-old boy is brought in by his parents, who are concerned about a delay in language development and unusual behavior. He was very irritable and difficult to feed as an infant, and started using single words at around 18-20 months of age, although he is yet to use two words together. He is currently in kindergarten and likes playing alone, only occasionally engaging with his parents at home. He also has difficulty maintaining eye contact. When he needs something, he pulls his parents towards the object and screams instead of pointing. He enjoys toys with wheels and always tries to line them up; when his toys are moved, he becomes irritable. He tends to flap his hands and stare at the ceiling lights. Intellectually, he performs age-appropriately. He has no history of seizures and is otherwise thriving well. There is no family history of behavioral or neurological disorders.
Social communication questionnaire (SCQ) score: 17
The MRI of the brain appears completely normal.
Frequency-specific auditory brainstem response testing shows no evidence of sensorineural hearing loss.
Skin examination with Wood's lamp shows no hypopigmented macules.