Early Diagnosis of Autism Spectrum Disorders
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Neonatal signs and symptoms may complement testing for genetic susceptibility to autism spectrum disorders. A 4-fold increased risk of autism has been reported in infants who had hyperbilirubinemia after birth.1 This came after a follow up of a prior study that found a 2-fold increased risk of autism in infants transferred to a neonatal ICU after delivery. Hyperbilirubinemia and poor feeding may play a role in the development of subsequent autism in premature infants; in extremely premature infants the incidence of subsequent autism may be as high as 27%.2 If they do play a role, we could then speculate—as Professor Thomas Hale, expert on breastfeeding pharmacology at Texas Tech (www.ibreastfeeding.com), suggested to me—that something in breast milk may protect us from autism analogous to omega-fatty acid, which protects us from retinal problems.3
The high incidence of later GI problems in children with autism could exacerbate nutritional changes. This perhaps explains why some children seem to respond to supplements, exclusion diets, or regimens that purportedly remove yeast from the GI tract. It would be ironic if the “gut-brain” connection, postulated by Dr Wakefield when promoting the autism-vaccine link, did have some validity as either an early marker or predisposing influence for children in whom autism develops.4
These potential influences of genetics and feeding/nutrition emphasize the concepts of multifactorial determination (many genes plus environmental factors) and gene-environmental interaction for complex disorders, such as autism spectrum disorder.2,5,6 Genetic changes in calcium-dependent synapse regulators focus attention on nutrients (eg, vitamin D and other heavy metals), whereas alterations in the oxytocin receptor or X-chromosome genes highlight “social hormones” and mediators of sex differences in autism.7 It is thus extremely important to view the term “autism” as shorthand for a vast spectrum of behaviors. Behaviors that potentially occur in any disorder with mental disability require experienced clinical correlation before any genetic test result is equated to an autism diagnosis or any single environmental factor (eg, thimerosal or measles, mumps, rubella vaccine) is incriminated as an autism cause.5,8
A view of autism as a single entity is a sad failing of research consortia and commercial laboratories who promote genetic testing; the former groups diverse patients in their genome association studies, the latter accumulates private patient databases and promotes prenatal diagnosis of autism based on a single genetic finding. A way of integrating the many genetic changes and potential environmental interactions that lead to autism is to explore central pathways that mediate the characteristic behaviors.
I agree with several observers that autism reflects deficits in the sensory nervous system—a hypothesis supported by its association with vision9 and hearing10 impairments and by its early expression as a sensory processing disorder.6 Severe neurologic disorders, such as Rett or fragile X syndrome, that cause global dysfunction naturally have deficits in communication and socialization. However, these conditions yield as much insight into autism as hydranencephaly does the neural basis of conscience.
Poor infant feeding caused by hypotonia or dysphagia can predict severe neurologic dysfunction along with autistic behaviors; however, neonatal differences in children with high-functioning autism could be more interesting. Perhaps alterations in olfaction, taste, or the hearing-vision-proprioception pathways that facilitate infant bonding could alter breastfeeding and contribute to later GI symptoms in children with autism. Included in these GI processes could be true gut-brain connections—the gut neural/hormone mediators that give feedback to the brain and are altered in disorders, such as Prader-Willi syndrome, with its high frequency of autism.2
Anyone reading the many reviews that lump numerous disorders under the umbrella of autism7 will cry out for the careful history, examination, differential diagnosis, and search for primary cause that are hallmarks of clinical medicine. Primary care physicians should include autism in their manifold burden not only because early suspicion will benefit their patients but also because their clinical observations and insights can contribute much to the objective diagnoses and treatments (pharmacogenomics) that are imminent. One area of therapy is early stimulation of neurosensory pathways, patterned after the treatment of strabismus, as suggested by an experienced pediatrician.11 I predict that some striking children will focus neuroimaging and genetic techniques on key scotomae of autism, as did the amnesiac H. M. for memory or the lobectomized Phineas Gage for behavior.12