Autism Spectrum Disorders
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- Group of neurodevelopmental disorders of early childhood characterized by (i) persistent deficits in social communication and interaction and (ii) restricted, repetitive patterns of behavior, interests, or activities
- DSM-5: umbrella term autism spectrum disorder (ASD), which encompasses a group of pervasive developmental disorders with designations for varying severities and associated symptoms
- ASD combines former diagnoses, including autistic disorder, childhood disintegrative disorder, Asperger disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), early infantile autism, childhood autism, Kanner autism, high-functioning autism, and atypical autism; many of which are still used by ICD-10 coding.
- Although symptoms must be present in the early development period, they may not be apparent until social demands exceed capacity.
- Symptoms must cause functional impairment.
- Severity levels
- Level 1: requiring support
- Level 2: requiring substantial support
- Level 3: requiring very substantial support
- Specifiers for associated symptoms include with catatonia; intellectual impairment; language impairment; known medical or genetic condition; and neurodevelopmental, mental, or behavioral disorders.
- Important to distinguish ASD from similar symptoms that could be better explained by intellectual disability or global developmental delay
- Incidence: estimated 1 in every 110 children in the United States diagnosed per year
- Predominant age: onset in early childhood
- Predominant sex: male > female (4:1)
Symptom onset can often be seen in children <3 years of age but may not become apparent until social demands exceed capacity.
- According to the Centers for Disease Control and Prevention (CDC) in 2014, an estimated prevalence of 1 in every 59 children between the ages of 3 and 17 years carried a diagnosis of ASD.
- This has been a steady increase since 2000 when the CDC reported the prevalence to be 1 in 150.
- Systematic literature reviews suggest changes in prevalence can be largely accounted for by changes in definition and increased awareness.
Etiology and Pathophysiology
- No single cause has been identified.
- General consensus: A genetic abnormality leads to altered neurologic development.
- No scientific evidence relating vaccines, such as vaccines for measles, mumps, rubella (MMR) or thimerosal causing ASDs
- Pathophysiology is not fully understood.
- Genetic concordance: A 2009 Swedish population-based cohort study of 2 million subjects showed a cumulative risk of 59% for monozygotic twins.
- Rate in siblings: 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 two or more affected children
- Male sex
- Family history
- Advanced paternal age
- Very low birth weight
- Maternal use of selective serotonin reuptake inhibitors (SSRIs) or valproate during pregnancy
- Note: Epidemiologic evidence does not support an association between immunizations and ASD.
- Screening for early intervention is associated with improved prognosis.
- Routine screening for ASD with a validated tool is recommended at 18- and 24-month well-child visits to assist with early detection.
Commonly Associated Conditions
- Intellectual disability
- 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, and fetal alcohol syndrome (rare)
- Seizures (increased risk if severe mental retardation)
- Sleep issues: insomnia, circadian rhythm sleep–wake disorder, sleep-related movement disorder
- Chronic constipation, diarrhea, abdominal pain