Autism - AccessScience from McGraw-Hill Education https://www.accessscience.com/content/autism/062850 (https://www.accessscience.com:443/) Article by: Byrd, Robert Department of Pediatrics, University of California Davis Medical Center, Sacramento, California. Publication year: 2014 DOI: http://dx.doi.org/10.1036/1097-8542.062850 (http://dx.doi.org/10.1036/1097-8542.062850) Content Characteristics, diagnosis, and etiology Treatments Bibliography Epidemiology Long-term outcomes Additional Readings A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism also can have unusual behaviors, such as insistence on sameness, obsessions, or stereotypic behaviors (for example, hand flapping, spinning, and toe walking). The condition varies greatly in the presenting symptoms, the timing of presentation, the range and severity of symptoms, and its association with other conditions. Although recognition of autism is increasingly more common, the cause of autism and the reason for its increase remain unknown. With intensive early intervention, significant improvements in a large percentage of children with autism can be achieved. See also: Developmental psychology (/content/developmental-psychology/189450); Nervous system (vertebrate) (/content /nervous-system-vertebrate/449300); Psychotherapy (/content/psychotherapy/555200) Characteristics, diagnosis, and etiology Autism is a spectrum disorder that also includes Asperger disorder, Rett syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS). Leo Kanner first described autism as a condition in 1943, but descriptions matching autism can be found throughout history. Based on his observation of 11 children, Kanner identified characteristic features of “early infantile autism” that are still considered essential in making an autism diagnosis. Three key features are (1) social impairments that affect how a person relates to other people, apparent early in life; (2) peculiar use of language—a failure to use language for interactive conversation; and (3) an “obsessive desire for the maintenance of sameness” associated with a “limitation in the variety of spontaneous activity.” Intelligence quotient (IQ) ranged from 50 to 70 in classic Kanner autism, but currently autism is recognized over a broader range of IQs. As recently as the late 1960s, autism was attributed to disturbed mother-child relationships. The term, “refrigerator mother,” represents a dark period in the history of autism, when misplaced blame was added to the anguish experienced by families with autistic children and delayed investigation into true causes. The recognition that 25% of children with autism developed seizures began the shift in thinking to the more current view that autism is a neurodevelopmental disorder with a biological basis. Finding the cause (or causes) of autism remains elusive, despite many advances in our understanding of factors associated with autism. Evidence continues to point strongly to genetic factors, but no single genetic factor or metabolic pathway has been associated with the majority of autism cases. Still, twin studies demonstrate concordance rates of 82–92% in identical twins and 1–10% in fraternal twins. Families with one child with autism are 35 times more likely to have another child with autism when compared to previously unaffected families. Autism occurs three to four times more frequently in males than in females. Autism is associated with many single gene mutations (for example, FMR1 in Fragile X, TSC1 or TSC2 in tuberous sclerosis, MECP2 in Rett syndrome, NF1 in neurofibromatosis, and PTEN in macrocephaly/autism syndrome), with certain 1 of 7 7/26/2016 5:30 AM Autism - AccessScience from McGraw-Hill Education https://www.accessscience.com/content/autism/062850 chromosomal rearrangements (for example, maternal duplication of 15q11-q13 involving the same chromosomal region that causes Prader-Willi and Angelman syndromes; trisomy 21 in Down syndrome), and with a growing list of genetic variants associated with increased autism risk in the form of autism susceptibility genes and copy number variations. However, a specific genetic association can be found in only 10–20% of children with autism. See also: Developmental genetics (/content/developmental-genetics/189400); Human genetics (/content/human-genetics/324600); Mutation (/content /mutation/441200) Autism often manifests after the first year of life, but many studies demonstrate prenatal and perinatal associations. Studies have found maternal antibrain antibodies in mothers of children with autism; these antibodies potentially could cross the placenta and alter fetal brain development. One study showed that 95% of a small sample of children with autism had elevated levels of four neuropeptides and neurotrophins in stored blood that was drawn for their newborn screen. In this study, elevated neurotrophin and neuropeptide levels were also found in children with mental retardation, but not in normal children or those with cerebral palsy. Specifically, the damage that occurs during pregnancy resulting in cerebral palsy does not produce the changes in blood spot data that were found in autism or mental retardation. Another study found that 42% of children with autism have posteriorly rotated ears (compared to 10% of children without autism), representing changes that occur in the first month of pregnancy. Other studies have shown differences in head size and brain structures. Head sizes of autistic children are on average normal at birth, and with age become larger than average. Specific brain structures are differentially affected. Some are larger than normal in autistic children, such as the hippocampus and amygdala, and some are smaller, such as the cerebellar vermis. The way that nerve cells or neurons are organized in the brain is different in some children with autism. Neurons in the brain are organized in minicolumns, and studies have shown thinning of minicolumns in the frontal and temporal regions of autistic brains when compared to control (normal) brains. Developmental delays, including speech delays, are often apparent early in the course of children with autism. See also: Brain (/content/brain/093200); Mental retardation (/content/mental-retardation/415100) Autism is currently diagnosed only through behavioral criteria. Typically, children with autism present with language delays, often first prompting a hearing assessment. Stereotypic behaviors, such as arm flapping, rocking, and spinning, usually develop later after communication and social impairments are apparent. About a third of parents of autistic children report regression of previously achieved milestones, and sometimes they attribute the loss of milestones to an identifiable stressor, such as the birth of a younger sibling or the receipt of a vaccination. Two-thirds of the children whose parents reported regression were noted to be developing normally on review of videotape taken around 12 months of age. The advantages of early diagnosis are many and generally outweigh concerns about potential harm from “labeling” a child. Pauline Filipek and colleagues have authored a consensus statement on the assessment of children suspected of having autism. Developmental surveillance should occur at well-child visits. Developmental concerns about speech, language, or social development warrant further evaluation. First-level evaluations include audiological assessments, lead testing (if indicated by pica behaviors), and screening tests that are specific for autism [for example, CHAT (Checklist for Autism in Toddlers) or the Autism Screening Questionnaire]. Children who screen positive for autism should be referred for a multidisciplinary assessment, which should include a detailed health and developmental history and a physical exam that looks for identifiable conditions that have autistic features. The history and physical findings should determine the necessity for additional laboratory and imaging studies. The assessment should include additional interviews and observations that specifically assess for autism. A complete evaluation also includes additional developmental screening and speech and language assessment, occupational therapy assessment, behavioral assessment, and a social work assessment. Other autism spectrum disorders (ASDs) retain many of the core features of autism. Deficits in communication and social interactions occur in Asperger syndrome, but to a lesser degree than autism. Significant delay in the onset or early course of language that is seen in autism is not seen in Asperger syndrome. Overall, affected children have a better facility with 2 of 7 7/26/2016 5:30 AM Autism - AccessScience from McGraw-Hill Education https://www.accessscience.com/content/autism/062850 language and more interest in social activities, but usually have autistic features, such as obsessive preoccupations. Rett disorder, primarily affecting females, has normal early development and then regression some time after five months. Girls with Rett syndrome typically carry a single gene marker, the MECP2 gene, and develop unsteady gait, loss or lack of language, constant hand-wringing and loss of functional use of their hands, social deficits, and mental retardation. Head sizes of affected children are on average normal at birth, but slowing of head growth during early development results in small head size. Childhood disintegrative disorder has normal