Autism Spectrum Disorders

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Description

  • Autism spectrum disorder (ASD) is a developmental disorder impacting roughly 1 in 59 children across the United States and other high-income countries. American Academy of Pediatrics (AAP), in contrast to the U.S. Preventive Services Task Force (USPSTF), recommends screening for ASD at 18 and 24 months of age. It is important to distinguish ASD from symptoms that could be better explained by other intellectual disability.
  • Symptoms must cause functional impairment; severity levels:
    • Level 1: requiring support—noticeable impairment
    • Level 2: requiring substantial support—marked deficits
    • Level 3: requiring very substantial support—severe impairments interfering with functionality

Epidemiology

Onset in early childhood; predominant sex: male > female, approximately 4:1 ratioPediatric Considerations
Symptom onset can often be seen in children <3 years of age but may not become apparent until social demands exceed capacity.

Prevalence

  • Estimated prevalence has increased from approximately 1.1% in 2008 to 2.3% in 2018 among children aged 8 years in the United States (1).
  • Higher prevalence contributed to changes in diagnostic criteria, increased awareness, improved ascertainment, and access to care (1).
  • Higher percentage of ASD observed in Black, Hispanic, and Asian and Pacific Islander children than in White children, which could reflect improvements in identification among these groups (1).

Etiology and Pathophysiology

  • No single cause has been identified. Variety of genetic and environmental factors have been associated with ASD, but none with absolute specificity for ASD development (1).
  • ASD has no association with immunization.

Genetics

  • Genetic concordance: A 2009 Swedish population-based cohort study of 2 million subjects showed a cumulative risk of 59% for monozygotic twins.
  • The American College of Medical Genetics and Genomics practice guidelines lists the risk of siblings of children diagnosed with ASD without an identifiable cause to be 7% if the affected child is female, 4% if the affected child is male, >30% if there are ≥2 affected children.

Risk Factors

  • Male sex, advanced paternal age, family history, very low birth weight
  • Perinatal insults including toxic exposures, teratogens, prenatal infections, use of selective serotonin reuptake inhibitors (SSRI) or valproate during pregnancy

General Prevention

  • Screening for early intervention is associated with improved prognosis, yet median age of diagnosis in the United States is >4 years.
  • Routine screening for ASD with a validated tool is recommended at 18- and 24-month well-child visits to assist with early detection.
  • Screening is indicated after 24 months if parents or clinician have concerns about ASD as less severe presentations may pass earlier routine screening.
  • Children with false positives for ASD frequently have some form of developmental disorder and benefit from early intervention.
  • Screening difficult due to variability of signs and symptoms of ASD and lack of unanimous consensus of social developmental milestones, thus leading to delayed diagnosis

Commonly Associated Conditions

  • Intellectual disability (seizure in severe cases)
  • Attention deficit hyperactivity disorder (ADHD), anxiety, depression, or obsessive behavior
  • Motor impairments including hypotonia, apraxia, toe walking, or gross motor delays
  • Phenylketonuria (PKU), tuberous sclerosis, fragile X syndrome, Angelman syndrome, Rett syndrome, CHARGE syndrome, Joubert syndrome, Smith-Lemli-Opitz syndrome, Timothy syndrome, and fetal alcohol syndrome (rare)
  • Sleep issues: insomnia, circadian rhythm sleep-wake disorder, sleep-related movement disorder
  • Change in bowel habits, abdominal pain

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