Deconstructing autism spectrum disorders: clinical perspective.

Autism spectrum disorder (ASD) is a term used to describe a heterogeneous group of children whose behaviorally defined characteristics overlap with the clinical manifestations of a variety of distinct behaviorally defined developmental disorders. ASD has many etiologies and strong but complex genetic and molecular underpinnings supporting genetic and phenotypic heterogeneity. Clinical and biological heterogeneity in ASD is consistent with the view of autism spectrum disorders as the expression of atypical brain development resulting in variable clinical manifestations that reflect differences in specific genetic and molecular pathways. It is likely that there are risk genes and early environmental risk factors for ASD that contribute to an altered trajectory of brain and behavioral development. These alterations are hypothesized to lead to altered social interaction and consequently to abnormal development of the neural networks critical for social and communicative interaction. This amplifies the abnormal socio-communicative developmental process leading to the full ASD syndrome. The hope is that interventions can alter these early developmental processes and put an infant back on a more typical developmental trajectory. In this discussion an overview of the limitations of the triad of behaviors used to diagnose ASD, specifically from the perspective of how these issues impact diagnosis and treatment of children with ASD will be presented and the clinical boundaries of the autism spectrum will be explored.