When Autistic Behavior Suggests a Disease Other than Classic Autism.

Most neurodevelopmental disorders are defined by their clinical symptoms and many disorders share common features. Recently there has been an increase in the number of children diagnosed with autism spectrum disorder, although concerns have been raised about the accuracy of the reported prevalence rates. This article reviews the essential features of autism spectrum disorder and describes other conditions that may include similar symptoms that may be misdiagnosed as autism spectrum disorder (primary communication disorders, anxiety disorders, attachment disorders, intellectual disability, vision and hearing impairment, and normal variations). An approach to differential diagnosis is discussed with particular attention to evaluation of young children.