Abstract
<p>Although the DSM diagnosis of autism spectrum disorder can be quite reliable, not all cases of autism are due to the polygenic and largely unresolved genetic architecture that characterizes the majority of idiopathic cases. The problem is that meeting diagnostic criteria, by itself, may tell the clinician remarkably little about why the child presents this way, what trajectory to expect, what comorbidities to be mindful of, what treatments may be disease-modifying rather than merely supportive, and what genetic or reproductive counseling the family might need. This article explores some of the neurological and neurodevelopmental disorders which can also manifest with surface symptoms within the autism spectrum (such as tuberous sclerosis complex, agenesis of the corpus callosum, very early term birth, uncorrected hydrocephalus, certain arachnoid cysts, fragile X syndrome, 22q11.2 deletion syndrome, Rett syndrome, Angelman syndrome, epileptic encephalopathy, Landau-Kleffner syndrome, and acquired brain injury early in development). A more in-depth series of investigations is also advised when there is a suspicion of additional neuropathology underlying the autism (such as obtaining a thorough developmental history, referral to a pediatric neurologist, lengthier EEG investigation, neuroimaging, and neuropsychological testing). Finally, it is emphasized that this population not infrequently warrants a more thorough investigation so that important (and potentially treatable) conditions that co-exist with the autism will not be missed.</p>