Autism spectrum disorder (ASD) is a serious neurodevelopmental condition that is diagnosed based on the presence and severity of core behavioral Symptoms- deficient social interactions, impaired communication, and the presence of repetitive behavior or restricted interests. In addition to the spectrum of symptoms seen within these principal diagnostic criteria, ASD individuals display a wide range of neurological comorbidities, including intellectual disability, epilepsy, and anxiety and mood disorders, as well as non-neurological comorbidities, including blood hyperserotonemia, immune dysregulation, and GI abnormalities.1,2 The striking clinical heterogeneity across individuals that share the same overall ASD diagnosis is consistent with the prevailing notion that the disorder has multiple underlying causes and developmental manifestations.
Several genetic and environmental susceptibility factors have been identified that increase the risk for features of autism, but few cases of ASD can be attributed to a defined etiology. Moreover, molecular diagnostics are not available for the reproducible identification of ASD; as yet, the disorder is diagnosed based on standardized behavioral assessments. Without a clear understanding of the mechanistic basis of ASD, therapeutics for treating the core symptoms of autism are limited; most drugs prescribed to ASD individuals are used to treat autism-related conditions, such as anxiety, hyperactivity, epilepsy, and obsessive-compulsive
behaviors. Collectively, the heterogeneity of ASD and the associated challenges in identifying specific causes, treatments, and molecular biomarkers for the disorder point to the need to better define the clinical subtypes of ASD and to tailor research studies to well-delineated subclasses of ASD individuals.
GASTROINTESTINAL PROBLEMS IN AUTISM
Of the many medical comorbidities associated with ASD, GI distress has gained significant attention because of its reported prevalence and association with symptom severity. Of the GI problems reported in subsets of autistic individuals, the most common are chronic constipation, diarrhea, and abdominal pain4–6 Gastroesophageal reflux, bloody stools, vomiting, and gaseousness are also elevated in some autistic individuals, as are signs of GI inflammation, such as lymphoid nodular hyperplasia, complement activation, and elevated pro-inflammatory cytokines, and intestinal pathologies, such as enterocolitis, gastritis, and esophagitis. Enteric immune abnormalities reported in ASD individuals suggest that GI dysfunction can contribute to the manifestation of core symptoms of autism.
