Autism Spectrum Disorders (ASD)

Basics

Neurodevelopmental disorders with early childhood onset.
Core features:
Persistent deficits in social communication and interaction.
Restricted, repetitive patterns of behavior, interests, or activities.
DSM-5 umbrella term combining autism, Asperger disorder, PDD-NOS, and related conditions.
Symptoms may not be obvious until social demands exceed capacity.
Severity levels:
Level 1: requiring support
Level 2: requiring substantial support
Level 3: requiring very substantial support

Onset typically <3 years, though diagnosis often delayed (>4 years).
Male predominance (~4:1).
Prevalence rising: ~2.3% of US children aged 8 years (2018 data).
Higher diagnosis rates in Black, Hispanic, Asian/Pacific Islander children due to improved ascertainment.

Multifactorial: genetic and environmental factors; no single cause identified.
No association with vaccines.
High genetic concordance: ~59% risk in monozygotic twins.
Sibling recurrence risk: 4% if affected male child, 7% if female, >30% if multiple affected siblings.
Risk factors: male sex, advanced paternal age, very low birth weight, prenatal exposures (SSRIs, valproate), infections, teratogens.

Early screening and intervention improve outcomes.
Recommended screening at 18 and 24 months during well-child visits.
Screening after 24 months if concerns persist.
Early intervention benefits even children with false-positive screening results.

Social-emotional reciprocity deficits: poor back-and-forth communication, reduced sharing of interests.
Nonverbal communication abnormalities: poor eye contact, gestures, facial expression.
Difficulty with relationships and peer interactions.
Restricted/repetitive behaviors: stereotyped movements, insistence on sameness, fixated interests.
Sensory hyper- or hyporeactivity.
Prenatal and developmental history, family history of autism/genetic disorders.

Growth parameters (macrocephaly in ~25%).
Vision, hearing, speech and communication assessment.
Neurologic exam and screening for dysmorphic/genetic features.
Red flags by age: no response to name (9 months), no interactive play (12 months), no pointing (18 months).

Anxiety, OCD, reactive attachment disorder.
Language disorders, intellectual disability, social communication disorder, ADHD.
Rett syndrome, fragile X, fetal alcohol syndrome.

Screening: M-CHAT(-R/F) at 18-24 months.
Additional tools: Infant-Toddler Checklist, STAT, ADI-R, ADOS-2.
Older children: Autism Spectrum Quotient-Child, Autism Spectrum Screening Questionnaire.
Genetic testing: chromosomal microarray, fragile X testing, whole exome sequencing.
Labs: CBC, TSH, creatine kinase, PKU screen; TORCH panel if indicated.
Imaging: MRI for focal neurologic symptoms.
EEG if seizures or specific developmental concerns.

Improve function and well-being.
Comprehensive treatment models (CTMs): early intensive behavioral interventions (ABA, TEACCH, ESDM).
Focused interventions: target specific skills, e.g., social communication.
Cognitive-behavioral therapy reduces anxiety in higher-functioning children.

Insufficient evidence to recommend dietary modifications (e.g., gluten-free, casein-free).

Influenced by IQ, early intervention, language skills, psychiatric comorbidities.
Lifelong need for structured support; some achieve independent living, employment, relationships.

Hirota T, King BH. Autism spectrum disorder: a review. JAMA. 2023;329(2):157-168.
Hyman SL, Levy SE, Myers SM, et al. Identification, evaluation, and management of children with autism spectrum disorder. Pediatrics. 2020;145(1):e20193447.