Autism Spectrum Disorders

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Basics

Description

  • 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
  • Diagnostic and Statistical Manual of Mental Disorders, 5th edition: 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

Epidemiology

  • Predominant age: onset in early childhood
  • Predominant sex: male > female (4:1)

Pediatric Considerations
Symptom onset can often be seen in children <3 years of age but may not become apparent until social demands exceed capacity.

Incidence
Estimated 1 in every 110 children in the United States diagnosed per year

Prevalence
  • 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.

Genetics
  • 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

Risk Factors

  • Male sex
  • Family history
  • Advanced paternal age
  • Very low birth weight
  • Perinatal insults including toxic exposures, teratogens, and prenatal infections.
  • Maternal use of selective serotonin reuptake inhibitors (SSRIs) or valproate during pregnancy
  • Note: Epidemiologic evidence does not support an association between immunizations and ASD.

General Prevention

  • Screening for early intervention is associated with improved prognosis, yet the 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 which also benefits from early intervention.
  • Screening can be difficult due to variability of signs and symptoms of ASD along with the lack of unanimous consensus of social developmental milestones, thus leading to delayed diagnosis.

Commonly Associated Conditions

  • Intellectual disability
  • 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)
  • Seizures (increased risk if severe mental retardation)
  • Sleep issues: insomnia, circadian rhythm sleep–wake disorder, sleep-related movement disorder
  • Chronic constipation, diarrhea, abdominal pain

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Basics

Description

  • 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
  • Diagnostic and Statistical Manual of Mental Disorders, 5th edition: 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

Epidemiology

  • Predominant age: onset in early childhood
  • Predominant sex: male > female (4:1)

Pediatric Considerations
Symptom onset can often be seen in children <3 years of age but may not become apparent until social demands exceed capacity.

Incidence
Estimated 1 in every 110 children in the United States diagnosed per year

Prevalence
  • 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.

Genetics
  • 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

Risk Factors

  • Male sex
  • Family history
  • Advanced paternal age
  • Very low birth weight
  • Perinatal insults including toxic exposures, teratogens, and prenatal infections.
  • Maternal use of selective serotonin reuptake inhibitors (SSRIs) or valproate during pregnancy
  • Note: Epidemiologic evidence does not support an association between immunizations and ASD.

General Prevention

  • Screening for early intervention is associated with improved prognosis, yet the 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 which also benefits from early intervention.
  • Screening can be difficult due to variability of signs and symptoms of ASD along with the lack of unanimous consensus of social developmental milestones, thus leading to delayed diagnosis.

Commonly Associated Conditions

  • Intellectual disability
  • 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)
  • Seizures (increased risk if severe mental retardation)
  • Sleep issues: insomnia, circadian rhythm sleep–wake disorder, sleep-related movement disorder
  • Chronic constipation, diarrhea, abdominal pain

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