Autism spectrum disorder

Last updated: October 5, 2022

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Autism spectrum disorder (ASD) encompasses the previously separate diagnoses of autistic disorder, Asperger disorder, childhood disintegrative disorder, and pervasive developmental disorder-not otherwise specified (PDD-NOS). ASD is a neurodevelopmental condition characterized by qualitative impairment in social interaction and communication as well as repetitive stereotyped behavior, interests, and activities. These features are present early in development and cause impairment of social and academic functioning. Diagnosis is based on careful assessment of behavior, cognitive development, and language skills. Treatment, which should be initiated early, involves educational and behavioral management, medical therapy, and family counseling.

  • Prevalence: 14.7/1000 in the US [1]
  • Sex: > (4:1)
  • Age: Symptoms typically manifest before 2–3 years of age-

References:[2]

Epidemiological data refers to the US, unless otherwise specified.

The etiology of autism spectrum disorder is complex and multifactorial. The following factors have been identified:

  • Genetics
    • Strong underlying predisposition
    • Many genes have been found to be associated with autism spectrum disorders
  • Environmental factors (e.g., toxin exposure, prenatal infections)
    • May increase the risk of ASD
    • However, no specific causes have been identified.

Studies have shown that there is no link between the MMR vaccine and autism.

References:[2]

Core features

  • Persistent impairment in communication and social interaction (e.g., inability to form relationships, abnormal language development, reduced empathy, difficulties in adjusting behavior to social situations, and poor eye contact)
  • Restricted, stereotyped patterns of behavior, interests, and activities (e.g., hand flapping, excessive touching/smelling, lining up toys, adverse response to sounds, and echolalia)
  • Repetitive movements (e.g., stereotyped hand movements)

Additional features

  • Intellectual impairment
  • Language impairment [3]
  • Sensory abnormalities (sensation can be hyporesponsive or enhanced) [4]

Mild ASD

  • No intellectual impairment
  • Affected individuals are able to speak in full sentences, read and write, and handle basic life skills
  • Symptoms may not become fully apparent until school age, when social impairments and stereotypies begin to exceed limited capabilities.
    • Impaired social communication and interaction (e.g., limited interest in social interaction, absent joint attention)
    • Insistence on sameness (e.g., eating specific foods in a particular order)
    • Fixated interest in unusual objects (e.g., ceiling fans)
    • Unusual responses to sensory stimuli (e.g., preferences for touching certain textures and strong aversions to others)
  • Affected individuals may develop strategies that mask deficits later in life.

Associated conditions

References:[6]

Differential diagnoses of impaired social interaction
Factor Autism spectrum disorder (ASD) Global developmental delay [7] Attention deficit hyperactivity disorder (ADHD) [8] Selective mutism [9] Rett syndrome [10] Hearing impairment
Age of onset
  • Before 2–3 years of age
  • Before 5 years of age
  • Usually before 6 years of age
  • Before 5 years of age
  • 7–24 months of age
  • Congenital or acquired later in life
Gender
  • Seen almost exclusively in girls
Motor skills
  • Normal
  • Normal
  • Loss of fine motor skills
  • Typical hand wringing
  • Normal
Language use
  • Impaired
  • Normal
  • Impaired
Behavior
  • Restricted, stereotyped patterns of behavior, interests, and activities
  • May show repetitive behaviors
  • Inattention and hyperactivity
  • Fails to speak in specific situations
  • Unusual eye movements
  • Sudden, odd facial expressions
  • Long bouts of laughter, hand licking, and grasping of hair or clothing
  • Not startled by loud sounds
  • Not turning head in direction of sounds
  • Communicates with hand gestures (e.g., pointing)
  • Temper tantrums
Physical features
  • Acceleration of head growth
  • May be abnormal depending on the etiology
  • Normal
  • May be abnormal depending on the etiology

The differential diagnoses listed here are not exhaustive.

  • Early behavioral and educational management
    • Should be started already in preschool (greatly improves outcomes)
    • Competence training: social skills, communication skills
    • Establishing clear and consistent structures
  • Family support and counseling (e.g., parental education on interaction with the child and acceptance of his/her behavior)
  • Medical treatment

Risperidone and aripiprazole are the only FDA-approved drugs for controlling irritability in patients with autism spectrum disorder.

References:[11][12]

  • Indicators of poor prognosis: severe core symptoms, cognitive impairment (low IQ), poor or absent language skills, late initiation of treatment
  • Impaired social interaction often persists into adulthood.
  • The majority of patients are dependent even as adults on their family and familiar surroundings.
  • Individuals with good language and cognitive ability usually learn to cope with their particularities.
  • Approx. 50% of individuals with language impairment do not develop the ability to speak.
  • Adolescents: Insensitive behavior towards peers often results in social exclusion.

References:[13]

  1. Augustyn M, Patterson MC, Bridgemohan C, Torchia MM. Autism Spectrum Disorder: Diagnosis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/autism-spectrum-disorder-diagnosis.Last updated: November 21, 2016. Accessed: May 26, 2017.
  2. Weissman L, Bridgemohan C, Augustyn M, Patterson MC, Torchia MM. Autism Spectrum Disorder in Children and Adolescents: Behavioral and Educational Interventions. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/autism-spectrum-disorder-in-children-and-adolescents-behavioral-and-educational-interventions.Last updated: November 21, 2016. Accessed: May 26, 2017.
  3. Weissman L, Bridgemohan C, Augustyn M, Patterson MC, Torchia MM. Autism Spectrum Disorder in Children and Adolescents: Pharmacologic Interventions. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/autism-spectrum-disorder-in-children-and-adolescents-pharmacologic-interventions.Last updated: October 5, 2016. Accessed: May 26, 2017.
  4. Weissman L, Bridgemohan C, Augustyn M, Patterson MC. Torchia MM. Autism Spectrum Disorder in Children and Adolescents: Overview of Management. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/autism-spectrum-disorder-in-children-and-adolescents-overview-of-management.Last updated: June 24, 2016. Accessed: May 26, 2017.
  5. Daroff RB, et al.. Bradley's Neurology in Clinical Practice. Elsevier
  6. Posar A, Visconti P. Sensory abnormalities in children with autism spectrum disorder. J Pediatr (Rio J). 2018; 94 (4): p.342-350. doi: 10.1016/j.jped.2017.08.008 . | Open in Read by QxMD
  7. Le T, Bhushan V,‎ Sochat M, Chavda Y, Abrams J, Kalani M, Kallianos K, Vaidyanathan V. First Aid for the USMLE Step 1 2019. McGraw-Hill Medical
  8. Mithyantha R et al.. Current evidence-based recommendations on investigating children with global developmental delay. Arch Dis Child. 2017; 102 (11): p.1071-1076. doi: 10.1136/archdischild-2016-311271 . | Open in Read by QxMD
  9. Matthews M et al.. Attention Deficit Hyperactivity Disorder. Springer Berlin Heidelberg ; 2013 : p. 235-266
  10. Hua A, Major N. Selective mutism. Curr Opin Pediatr. 2016; 28 (1): p.114-120. doi: 10.1097/mop.0000000000000300 . | Open in Read by QxMD
  11. Gold WA et al.. Rett Syndrome: A Genetic Update and Clinical Review Focusing on Comorbidities. ACS Chemical Neuroscience. 2017; 9 (2): p.167-176. doi: 10.1021/acschemneuro.7b00346 . | Open in Read by QxMD
  12. Augustyn M, Patterson MC, Bridgemohan C, Torchia MM. Autism Spectrum Disorder: Terminology, Epidemiology, and Pathogenesis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/autism-spectrum-disorder-terminology-epidemiology-and-pathogenesis.Last updated: March 7, 2017. Accessed: May 26, 2017.
  13. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. undefined. 2013 . doi: 10.1176/appi.books.9780890425596 . | Open in Read by QxMD

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