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Key Features

  • A neurologic disorder characterized by

    • Persistent deficits in social communication and social interaction across multiple contexts

    • Restricted, repetitive patterns of behavior, interests, or activities

  • Occur in approximately 1 in 68 children

  • Males are overrepresented by about 5:1

  • No known etiology can be found in 80–90% of cases

  • A genetic syndrome such as fragile X syndrome or chromosome 15q duplication is found in 10–20% of cases

Clinical Findings

  • Often not diagnosed until age 3–4 years, when disturbances in reciprocal social interaction and communication become more apparent

  • However, impairments in communication and behavior can often be recognized in the first 12–18 months of life

  • Most common early characteristics are a consistent failure to orient to one's name, regard people directly, use gestures, and to develop speech

  • Even if one of these skills is present, it is often diminished in frequency, inconsistent, or fleeting

  • Sharing affect or enjoyment is an important precursor to social interaction

    • By 16–18 months a child should have "joint attention," which occurs when two people attend to the same thing at the same time

    • This is usually accomplished by shifting eye gaze, pointing, or saying "look"

    • Toddlers should regularly point to get needs met ("I want that") and to show ("look at that") by 1 year of age

    • By 18 months a toddler should be able to follow a point, imitate others, and engage in functional play (using toys in the way that they are intended to be used, such as rolling a car, throwing a ball, or feeding a baby doll)

  • Restricted interests and repetitive behaviors sometimes do not emerge until after age 2, but usually are present before age 2


  • There is mounting evidence that a diagnosis of ASD can be made reliably by age 2 years and is stable over time

  • The Modified Checklist for Autism in Toddlers—Revised with Follow up (M-CHAT-R/F) is designed for children 16–30 months of age

  • An autism-specific screen is recommended at 18 and 24–30 months because some of the symptoms may be more obvious in an older child and because about 30% of children with ASDs experience a regression or plateau in skills between 12 and 24 months

  • All children with ASD should have a formal audiology evaluation

  • Laboratory tests such as an array comparative genomic hybridization (aCGH) and a DNA for fragile X syndrome should be considered

  • Metabolic screening, lead level, and thyroid studies may also be done if indicated by findings in the history and physical examination

  • A Wood lamp examination for tuberous sclerosis is also recommended

  • Neuroimaging

    • Not routinely indicated even in the presence of mild/relative macrocephaly because children with autism often have relatively large heads

    • Should be done if microcephaly or focal neurologic signs are noted

  • When there is history of regression,

    • An overnight EEG should be considered to rule out electrical status epilepticus in sleep

    • Metabolic testing and an ...

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