Autism Spectrum Disorders – Causes, Symptoms, Diagnosis, Treatment and Ongoing care



Group of neurodevelopmental disorders of early childhood

  • Includes autistic disorder, Rett disorder, childhood disintegrative disorder, Asperger disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS)
  • Autistic disorder includes classic autism and childhood autism.
  • Rett disorder involves mutations in the MECP2 gene. Mostly in females with initial normal development until approximately 18 months of age with microcephaly and dementia.
  • Childhood disintegrative disorder: Regression after at least 2 years of normal development
  • Asperger disorder: Better development with mechanics of verbal expression, higher levels of cognition and interest in social activity
  • PDD-NOS: Meet some, but not all of DSM-IV-TR criteria for autistic disorder
  • Characterized by:
    • Impairment of effective social skills
    • Absent or impaired communication skills
    • Repetitive and/or stereotyped behaviors and interests, especially in inanimate objects
    • System(s) affected: Nervous


  • Predominant age: Onset in early childhood
  • Predominant sex: Male > Female (4:1) except for Rett disorder

Pediatric Considerations

Symptom onset seen in children <3 years (except for childhood disintegrative disorder)


Estimated 1/100 to 1/500 children

Risk Factors

Siblings with autism have shown to have a 5× greater risk of developing autism. Prevalence ranging from 2% to 8%.

Pregnancy Considerations

Siblings with autism have shown to have a 5× greater risk of developing autism. Prevalence ranging from 2% to 8%.


  • High concordance in monozygotic twins
  • Increased recurrence risk (3–7%) in subsequent siblings

General Prevention

  • Early screening for early treatment = better prognosis.
  • Some ASDs such as Rett disorder are known to be caused by genetic mutations.


Pathophysiology is incompletely understood.


  • No single cause has been identified.
  • General consensus: A genetic abnormality leads to altered neurologic development.
  • Research continues to investigate the links between heredity, genetics, and medical problems.
  • No documented scientific evidence exists that proves vaccines or thimerosal cause ASDs.

Commonly Associated Conditions

  • Mental retardation
  • Attention deficit/hyperactivity disorder (ADHD)
  • Phenylketonuria (PKU), tuberous sclerosis, fragile X syndrome, Angelman syndrome, and fetal alcohol syndrome (rare)
  • Anxiety
  • Depression
  • Obsessive behavior
  • Seizures (increased risk if severe mental retardation)

Asperger syndrome, Autism, Autism spectrum, Childhood disintegrative disorder, Rett syndrome, PDD-NOS, childhood disintegrative disorder, monozygotic twins,



  • Impairment in social interaction:
    • Impairment in nonverbal behaviors such as eye- to-eye gaze, facial expression
    • Unable to develop peer relationships
    • Does not smile nor share emotions
    • Loss of social or emotional reciprocity
  • Communication impairment:
    • Delay or lack of development in language skills
    • Inability to initiate or sustain conversation
    • Stereotyped and repetitive use of language
    • Preoccupation with parts of toys or body parts
  • Repetitive and stereotyped patterns of behavior:
    • Excessively lines up toys or other objects
    • Unusually attached to 1 particular toy or object
    • Repetitive odd movements (toe walking, hand flapping)
    • Adherence to specific routines or rituals
  • Asperger disorder does not have clinically significant delays in cognitive development, language acquisitions, nor learning/adaptive skills.
  • Rett disorder is predominantly in females without macrocephaly.
  • Childhood disintegrative disorder with normal development until 2 years of age
  • PDD-NOS does not meet DSM-IV-TR criteria for autism.
  • Prenatal, neonatal, and developmental history
  • Seizure disorder
  • Family history of autism, genetic disorders, learning disabilities, psychiatric illness, neurological disorders, genetic disorders, or mental retardation

Physical Exam

  • Macrocephaly in 25% (except in Rett syndrome); head circumference growth peaks at age 6 months and begins to decline by 1 year.
  • Dysmorphic features consistent with genetic disorder (fragile X syndrome)
  • Hypotonia can occur in autism, but neurological deficit is a sign that imaging may be needed.
  • Wood lamp skin exam to rule out tuberous sclerosis

Diagnostic Tests & Interpretation

  • Checklist for Autism in Toddlers (CHAT) to screen for ASDs at 18 months of age. (To order:
  • The Pervasive Developmental Disorders Screening Test-II (PDDST-II) to screen for ASDs beginning at 18 months
  • Modified Checklist for Autism in Toddlers (M-CHAT) to screen for ASDs at 16–30 months
  • Social Communication Questionnaire (SCQ) (formerly Autism Screening Questionnaire)—used with children age 4 years and older—the gold-standard diagnostic interview used in research studies


  • Lead screening
  • PKU screening
  • Karyotype and DNA analysis (fragile X, PKU, tuberous sclerosis, and others)
  • Metabolic testing if signs of:
    • Lethargy, limited endurance
    • Hypotonia
    • Recurrent vomiting and dehydration
    • Developmental regression
    • Unusual habits
    • Specific food intolerance

Follow-Up & Special Considerations

  • Hearing tests: Audiometry and BAERS
  • Comprehensive speech and language evaluation
  • Evaluation by multidisciplinary team: Includes a psychiatrist, neurologist, psychologist, speech therapist, and other autism specialists
  • Intellectual level needs to be established and monitored, as it is one of the best measures of prognosis.
  • Test used to follow autism are:
    • Autism Behavior Checklist (ABC)
    • Gilliam Autism Rating Scale (GARS)
    • Childhood Autism Rating Scale (CARS)
    • Autism Diagnosis Interview-Revised (ADI-R)
    • Autism Diagnostic Observation Schedule-Generic (ADOS-G) Imaging


Initial approach

Magnetic resonance imaging (MRI) useful only if focal neurologic symptoms

Diagnostic Procedures/Surgery

Electroencephalogram (EEG) only if history of seizures or spells

Differential Diagnosis

Other mental and central nervous system (CNS) disorders:

  • Obsessive-compulsive disorder
  • Elective mutism
  • Language disorder/hearing impairment
  • Intellectual disability/global developmental delay
  • Stereotyped movement disorder
  • Severe early deprivation/reactive attachment disorder
  • Anxiety disorder
  • Developmental language disorder


Support's development and hosting


Medical causes of autistic-like behavior should be excluded with behavioral management maximized prior to considering medication with symptom-specific therapy, as pharmacological therapy data are scant.

First Line

  • No true 1st-line medical therapy
  • Stimulant medications (such as methylphenidate): Efficacious in treating concomitant symptoms of attention deficit disorder, such as impulsiveness, hyperactivity, and inattention; however, the magnitude of response is less than in typically developing children, and adverse effects are more frequent.
  • Selective serotonin reuptake inhibitors (SSRIs) have shown some help in reducing ritualistic behavior and improving mood and language skills. Initial choice for anxiety and depressive mood. Also administered for dysregulated mood (1).
  • Risperidone (an atypical antipsychotic) has been shown to be effective for short-term treatment of tantrums, aggression, and self-injurious behavior. Improvements in stereotyped behavior, hyperactivity, irritability, repetitious behaviors, and social withdrawal have also been noted (2)[A]. Precautions: Causes weight gain as an adverse effect. Associated with sedation, dry mouth, agitation enuresis, dyspepsia, diarrhea, constipation, and tremor.

Second Line

Vitamin B6 and magnesium with inconclusive evidence in improving speech and language (3,4)[C].

Additional Treatment

General Measures

  • Comprehensive structured educational programming of a sustained and intensive design, most commonly applied behavioral analysis therapy
  • Core features of a successful education program:
    • High staff–student ratio 1:2 or less
    • Individualized programming
    • Specialized teacher training with ongoing evaluation of teachers and programs
    • 25 hours a week minimum of specialized services
    • A structured routine environment that emphasizes attention, imitation, communication, socialization, and play interactions
    • Functional analysis of behavioral problems
    • Transition planning and involvement of the family
  • Currently no cure for ASDs. Early diagnosis and initiation of multidisciplinary intervention help enhance functioning in later life.
  • Early intervention for ages 3 and under
  • School-based special education for older children
  • Find alternative methods of communication: Sign language; picture exchange communication system

Issues for Referral

  • Refer early to:
    • Early learning for evaluation of behavior and language
    • Genetic counseling
    • Audiology
  • Consider referrals to psychiatry, ophthalmology, otolaryngology, neurology, and nutrition
  • Refer family members to parent support groups and respite programs

Complementary and Alternative Medicine

  • Music therapy has been shown to improve communication skills in autistic patients with limited data (5)[B].
  • Auditory integration training is used for autistic children with sound sensitivity (6)[B].
  • Osteopathic manipulative therapy (OMT) has been shown to improve sensory and motor performance with neurological problems, including autism. Treatment that starts before the age of 2 years showed the greatest effect (7)[C].

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

  • Constant by caregivers
  • Reevaluation every 6–12 months by physician for seizures, sleep and nutritional problems, and prescribed medical management
  • Intellectual and language testing every 2 years in childhood


Gluten- and casein-free diets show some reduction in autistic traits; however, large-scale, good-quality randomized controlled trials are needed (8).

Patient Education

  • Autism Society of America:
  • The Centers for Disease Control and Prevention, Autism Info. Center:
  • The Centers for Disease Control and Prevention, “Learn the Signs. Act Early”:
  • First Signs:
  • Autism Speaks:
  • Supplemental security income:
  • Autism and vaccines:


  • Those who begin treatment at a young age (2–4 years) have significantly better outcomes.
  • Prognosis is closely related to initial intellectual abilities, with only 20% functioning above the mentally retarded level.
  • Communicative language development before 5 years is also associated with a better outcome.
  • The general expected course is for a lifelong need for supervised structured care.


  • Increasing incidents of seizure disorders in up to 1 in 4 children.
  • Increased risk for physical and sexual abuse
  • If pica, increased risk of lead poisoning
  • Limited variety of food consumed due to dietary obsessions
  • Increased risk for gastrointestinal symptoms, including weight abnormalities and abnormal stool patterns


1. Selective serotonin reuptake inhibitors (SSRIs) for autism spectrum disorders (ASD). Williams, Katrina. Wheeler, Danielle M. Silove, Natalie. Hazell, Philip. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic Reviews. 8, 2010.

2. Risperdone for autistic spectrum disorder. Jesner, Ora S. Aref-Adib, Mehrnoosh. Coren, Esther. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic Reviews. 1, 2009.

3. Vitamin B6 for cognition. Malouf, Reem. Grimley Evans, John. Cochrane Dementia and Cognitive Improvement Group Cochrane Database of Systematic Reviews. 1, 2009.

4. Combined vitamin B6-magnesium treatment in autism spectrum disorder. Nye, Chad. Brice, Alejandro. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic Reviews. 1, 2009.

5. Music therapy for autistic spectrum disorder. Gold, Christian. Wigram, Tony. Elefant, Cochavit. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic. Reviews. 1, 2009.

6. Auditory integration training and other sound therapies for autism spectrum disorders. Sinha, Yashwant. Silove, Natalie. Wheeler, Danielle M. Williams, Katrina J. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic Reviews. 1, 2009.

7. Frymann VM, Carney RE, Springall P. Effect of osteopathic medical management on neurologic development in children. J Am Osteopath Assoc. 1992;92:729–44.

8. Gluten- and casein-free diets for autistic spectrum disorder. Millward, Claire. Ferriter, Michael. Calver, Sarah J. Connell-Jones, Graham G. Cochrane Developmental, Psychosocial and Learning Problems Group Cochrane Database of Systematic Reviews. 1, 2009.

Additional Reading

See Also (Topic, Algorithm, Electronic Media Element)

Algorithm: Mental Retardation



  • 299.00 Infantile autism, current or active state
  • 299.10 Disintegrative psychosis, current or active state
  • 299.80 Other specified early childhood psychoses, current or active state
  • 299.90 Unspecified childhood psychosis, current or active state
  • 330.8 Other specified cerebral degenerations in childhood


  • 408856003 Autistic disorder (disorder)
  • 71961003 childhood disintegrative disorder (disorder)
  • 23560001 Asperger’s disorder (disorder)
  • 35919005 pervasive developmental disorder (disorder)
  • 68618008 Rett’s disorder (disorder)

Clinical Pearls

ALARM mnemonic from the American Academy of Pediatrics (AAP):

  • Autism spectrum disorder is prevalent (screen ALL children between 18–24 months).
  • Listen to parents when they feel something is wrong.
  • Act early: Screen all children who fall behind in language and social developmental milestones (use early learning to help with evaluation).
  • Refer to multidisciplinary teams (speech and language evaluation, genetic screening, social support groups).
  • Monitor support for patient and families.

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