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Autism Spectrum Disorders.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2015.
2003 Aug 27 [updated 2010 Apr 13].



Autism comprises a clinically heterogeneous group of disorders – collectively referred to as “autism spectrum disorders” (ASD) – that share common features of impaired social relationships, impaired language and communication, and repetitive behaviors or a narrow range of interests. For most children with autism, symptoms develop gradually, although approximately 30% have a "regressive" onset usually between ages 18 and 24 months. About 50%-70% of children with autism are identified as intellectually disabled by nonverbal IQ testing and approximately 25% develop seizures. Autism can be considered complex (i.e., presence of dysmorphic features and/or microcephaly) or essential (i.e., absence of physical abnormalities and microcephaly). About 25% of children who fit the diagnostic criteria for ASD at age two to three years subsequently begin to talk and communicate, and by age six to seven years blend to varying degrees into the regular school population. The remaining 75% have lifelong disability requiring intensive parental, school, and social support.


The behavioral criteria presented in the American Psychiatric Association Manual of Psychiatric Diseases, 4th edition (DSM-IV) remain the standard for making an autism diagnosis in the US. Currently, three subgroups (autistic disorder, Asperger syndrome, and PDD-NOS) are recognized. To qualify for a diagnosis of autistic disorder (i.e., classic autism), a child must have shown abnormalities in social interaction and language used for social communication or symbolic/imaginative play and either stereotypic motor mannerisms or restricted patterns of interest before age three years. If the child does not meet criteria for autistic disorder, he or she may be given a diagnosis of Asperger syndrome (AS) or pervasive developmental disorder-not otherwise specified (PDD-NOS), the other two disorders included in ASD. Autism has many etiologies, a concept that was widely embraced following the discovery of the molecular basis of Rett syndrome in 2006. Since then autism has been documented in hundreds of neurologically based syndromes with multiple causes, outcomes, and treatment responses. Currently, an etiology can be identified for between 15% and 20% of individuals with autism; in the others the cause remains unknown.


For individuals with autism in whom the etiology is known, genetic counseling and risk assessment are based on the genetics of that specific diagnosis. For autism of unknown cause, the empiric aggregate risk to sibs is 5%-10% for autism and 10%-15% for milder conditions, including language, social, and psychiatric disorders. For families with two or more affected children, the recurrence risk approaches 35%. Male sibs (brothers) of a proband with essential autism have a 7% risk for autism and an additional 7% risk for milder ASD. Female sibs (sisters) of a proband with essential autism have a 1% risk for autism; the risk for a milder ASD is unknown. The recurrence risk to sibs of a proband with complex autism is 1% for autism and an additional 2% for a milder ASD.


Treatment of manifestations: Management of autism involves educational, behavioral, and medical therapies to promote conversational language and social interactions while mitigating repetitive self-stimulatory behaviors, tantrums, aggression, and self-injurious behaviors. The mainstay of therapy is early individualized intensive training either in the school or home, where the environment must be predictable with planned transitions between activities and venues. Visual supports are helpful in promoting language acquisition. The Visually Cued Instruction and Schedules program uses graphic clues to aid communication, organizational skills, and self-management. The Picture Exchange Communication System provides a visual system in which to learn communication. Social Stories intervention increases appropriate behavior by explaining social situations in ways understandable to the student. Medications, especially atypical antipsychotics, can ameliorate specific symptoms such as aggressive or self-injurious behavior. Children treated early can usually be taught, to varying degrees, to communicate, recognize and respond to social interactions, develop imaginative play, and curb all-consuming repetitive self-stimulatory behaviors. Prevention of secondary complications: Intensive behavioral intervention programs can prevent or at least mitigate aggressive behaviors (tantrums, aggression, and self injurious behaviors) that occur commonly in children with no communication skills or interest in social interactions. Surveillance: At least annual surveillance for health, developmental progress, education milestones, behavioral and family functioning preferably at a multidisciplinary autism clinic is strongly recommended. Evaluation of relatives at risk: Because sibs are at increased risk of developing autism or an ASD, their language, development, and behavior should be closely monitored for the first three years, preferably through an autism sib program.

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