Summary
Autism spectrum disorder (ASD) encompasses the previously separate diagnoses of autistic disorder, Asperger disorder, childhood disintegrative disorder, and pervasive developmental disorder-not otherwise specified (PDD-NOS). ASD is a neurodevelopmental condition characterized by qualitative impairment in social interaction and communication as well as repetitive stereotyped behavior, interests, and activities. These features are present early in development and cause impairment of social and academic functioning. Diagnosis is based on careful assessment of behavior, cognitive development, and language skills. Treatment, which should be initiated early, involves educational and behavioral management, medical therapy, and family counseling.
Epidemiology
- Prevalence: 14.7/1000 in the US [1]
- Sex: ♂ > ♀ (4:1)
- Age: Symptoms typically manifest before 2–3 years of age.
References:[2]
Epidemiological data refers to the US, unless otherwise specified.
Etiology
The etiology of autism spectrum disorder is complex and multifactorial. The following factors have been identified:
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Genetics
- Strong underlying predisposition
- Many genes have been found to be associated with autism spectrum disorders
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Environmental factors (e.g., toxin exposure, prenatal infections)
- May increase the risk of ASD
- However, no specific causes have been identified.
Studies have shown that there is no link between the MMR vaccine and autism.
References:[2]
Clinical features
Core features
- Persistent impairment in communication and social interaction (e.g., inability to form relationships, abnormal language development, reduced empathy, difficulties in adjusting behavior to social situations, and poor eye contact)
- Restricted, stereotyped patterns of behavior, interests, and activities (e.g., hand flapping, excessive touching/smelling, lining up toys, adverse response to sounds, and echolalia)
- Repetitive movements (e.g., stereotyped hand movements)
Additional features
- Intellectual impairment
- Language impairment [3]
- Sensory abnormalities (sensation can be hyporesponsive or enhanced) [4]
Mild ASD
- No intellectual impairment
- Affected individuals are able to speak in full sentences, read and write, and handle basic life skills
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Symptoms may not become fully apparent until school age, when social impairments and stereotypies begin to exceed limited capabilities.
- Impaired social communication and interaction (e.g., limited interest in social interaction, absent joint attention)
- Insistence on sameness (e.g., eating specific foods in a particular order)
- Fixated interest in unusual objects (e.g., ceiling fans)
- Unusual responses to sensory stimuli (e.g., preferences for touching certain textures and strong aversions to others)
- Affected individuals may develop strategies that mask deficits later in life.
Associated conditions
- Epilepsy
- Other neurodevelopmental and psychiatric disorders, e.g., ADHD, Pica, anxiety disorder
- Genetic disorders, e.g., tuberous sclerosis, fragile X syndrome, Rett syndrome
- Associated with a higher head circumference to brain volume ratio [5]
Diagnosis
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Comprehensive evaluation of
- Social interaction and communication skills
- Language and comprehension skills
- Behavior
- Cognitive development
- Associated conditions
- Hearing and vision testing: to rule out comorbidities or other causes of developmental delays and behavioral disorders.
- Genetic testing: fragile X syndrome, tuberous sclerosis (if any of these conditions is suspected)
References:[6]
Differential diagnoses
| Differential diagnoses of impaired social interaction | ||||||
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| Factor | Autism spectrum disorder (ASD) | Global developmental delay [7] | Attention deficit hyperactivity disorder (ADHD) [8] | Selective mutism [9] | Rett syndrome [10] | Hearing impairment |
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The differential diagnoses listed here are not exhaustive.
Treatment
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Early behavioral and educational management
- Should be started already in preschool (greatly improves outcomes)
- Competence training: social skills, communication skills
- Establishing clear and consistent structures
- Family support and counseling (e.g., parental education on interaction with the child and acceptance of his/her behavior)
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Medical treatment
- SSRIs: repetitive stereotyped behavior, anxiety
- Antipsychotic drugs: aggression, self-injury
- Methylphenidate: ADHD
Risperidone and aripiprazole are the only FDA-approved drugs for controlling irritability in patients with autism spectrum disorder.
References:[11][12]
Prognosis
- Indicators of poor prognosis: severe core symptoms, cognitive impairment (low IQ), poor or absent language skills, late initiation of treatment
- Impaired social interaction often persists into adulthood.
- The majority of patients are dependent even as adults on their family and familiar surroundings.
- Individuals with good language and cognitive ability usually learn to cope with their particularities.
- Approx. 50% of individuals with language impairment do not develop the ability to speak.
- Adolescents: Insensitive behavior towards peers often results in social exclusion.
References:[13]