Autism Spectrum Disorder (ASD)
Persistent deficits in social communication plus restricted/repetitive behaviors present in early development.
Also known as: autism, ASD, autism spectrum disorder
Overview
A neurodevelopmental disorder characterized by persistent deficits in social communication and social interaction across multiple contexts AND restricted, repetitive patterns of behavior, interests, or activities, with symptoms present in early developmental period and causing clinically significant impairment.
Epidemiology
Prevalence ~1 in 36 US children (CDC 2023). Male-to-female ratio ~4:1, though females may be underdiagnosed. Highly heritable (~80%).
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Risk factors
- Male sex; sibling with ASD (recurrence risk ~10-20%)
- Advanced parental age
- Prematurity, low birth weight, perinatal complications
- Genetic syndromes: fragile X, tuberous sclerosis, Rett (girls), 22q11.2 deletion
- Valproate exposure in utero
Pathophysiology
Polygenic and copy-number variant contributions; abnormal cortical development and connectivity, particularly in regions subserving social cognition and language. Synaptic and neurodevelopmental gene pathways implicated.
Clinical presentation
Symptoms
- Social communication: reduced social-emotional reciprocity, atypical nonverbal communication, difficulty developing and maintaining relationships appropriate to developmental level
- Restricted/repetitive: stereotyped/repetitive motor movements or speech, insistence on sameness/routines, highly restricted fixated interests, hyper- or hyporeactivity to sensory input
- Variable language ability — from non-speaking to fluent; pragmatic deficits common even in fluent speakers
- Common co-occurrences: ID, ADHD, anxiety, epilepsy, GI symptoms, sleep disorders
Signs / physical exam
- Reduced eye contact, limited joint attention, atypical play (lining up toys, lack of pretend play)
- Echolalia, scripted speech
- Hand-flapping, rocking, toe-walking
- Sensory sensitivities (sound, texture, light)
Differential diagnosis
- Intellectual disability without ASD — Cognitive impairment without disproportionate social communication deficits
- Language disorder / social communication disorder — Language or pragmatic deficits without restricted/repetitive behaviors
- ADHD — Inattention and impulsivity without core social-communication impairment; commonly co-occurs
- Reactive attachment disorder — History of severe neglect; social withdrawal improves with stable caregiving
- Selective mutism — Speaks at home but not in select settings; otherwise typical social development
- Hearing impairment — Screen audiology in any child with language delay
- Anxiety / OCD — Distinguish ego-dystonic compulsions from autistic restricted interests, which are typically ego-syntonic
Diagnostic workup
Diagnostic criteria
DSM-5-TR: (A) Persistent deficits in social communication and interaction across contexts — all three subcriteria (reciprocity, nonverbal communication, relationships); (B) Restricted/repetitive patterns — >=2 of four (stereotypies, insistence on sameness, restricted interests, sensory differences); (C) Symptoms in early developmental period; (D) Clinically significant impairment; (E) Not better explained by ID alone. Specify severity (levels 1-3 by support needs), with/without ID, language impairment, medical/genetic conditions, or catatonia. Screening: M-CHAT-R/F at 18 and 24 months.
Labs
- Screen lead level, audiology evaluation
- Genetic evaluation: chromosomal microarray and fragile X testing recommended for all; consider whole exome based on dysmorphology
- Metabolic workup if regression or dysmorphic features
- EEG if seizures suspected
Imaging
- MRI not routine; obtain if focal findings, regression, microcephaly, or macrocephaly with neurologic signs
Diagnostic algorithm
| ASD Severity | Social communication | Restricted/repetitive | Support need |
|---|---|---|---|
| Level 1 | Difficulty initiating; atypical responses | Inflexibility hampers function | Requiring support |
| Level 2 | Marked deficits even with supports | Distress with change; obvious to observer | Substantial support |
| Level 3 | Severe deficits in functional communication | Extreme inflexibility, marked impairment | Very substantial support |
Treatment
First-line
- Early intensive behavioral intervention — applied behavior analysis (ABA), naturalistic developmental behavioral interventions (NDBI), Early Start Denver Model
- Speech-language therapy; occupational therapy for sensory and motor issues
- Educational supports — IEP, structured teaching
- Family support and psychoeducation; respite care
- Treat co-occurring conditions: ADHD, anxiety, sleep, epilepsy
Second-line / adjunct
- Atypical antipsychotic — risperidone or aripiprazole (FDA-approved) for irritability/aggression/self-injury
- SSRI for comorbid anxiety/OCD (avoid in repetitive behaviors alone — limited evidence)
- Melatonin for sleep onset
- Stimulants/non-stimulants for comorbid ADHD (response often less robust than in non-ASD ADHD)
Complications
- Co-occurring intellectual disability (~30%), epilepsy (~20-30%), anxiety/OCD, ADHD, depression
- Self-injurious behavior in severe cases
- Sleep and feeding difficulties
- Wandering/elopement
- Higher rates of suicidality, especially in adults with ASD without ID
- Caregiver burden
PANCE pearls
- All children should be screened for ASD at 18 and 24 months using M-CHAT-R/F per AAP; refer for diagnostic evaluation if positive — do not wait.
- Early intervention before age 3 produces the largest gains; do not delay services for formal diagnosis.
- Catatonia is increasingly recognized in adolescents/adults with ASD — consider in regression with mutism, posturing.
- Adults with ASD often present first with anxiety or depression; ask about lifelong social communication patterns.
References
- AAP 2020 — Hyman SL et al. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics 2020
- AACAP 2014 — AACAP Practice Parameter for the Assessment and Treatment of Children, Adolescents, and Adults with ASD (2014)
- DSM-5-TR — American Psychiatric Association. DSM-5-TR (2022)
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