Autism spectrum disorders are neurodevelopmental disorders characterized by impaired social interaction and communication, repetitive and stereotyped patterns of behavior, and uneven intellectual development often with intellectual disability. Symptoms begin in early childhood. The cause in most children is unknown, although evidence supports a genetic component; in some patients, the disorders may be caused by a medical condition. Diagnosis is based on developmental history and observation. Treatment consists of behavioral management and sometimes drug therapy.

Autism, a neurodevelopmental disorder, is the most common of the disorders called autism spectrum disorders (ASD) or pervasive developmental disorders (PDD—see Table 2: Learning and Developmental Disorders: Autism Spectrum Disorders). Current estimates of prevalence of ASD are in the range of 1/88. Autism is 2 to 4 times more common among boys. In recent years, there has been a rapid rise in the diagnosis of ASD, partially because of changes in diagnostic criteria.

Table 2
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Autism Spectrum Disorders Subtype Characteristics Asperger syndrome Language and cognition generally better than in autism Socially isolated and often viewed as odd or eccentric Clumsiness Repetitive patterns of behavior, interests, and activities Atypical sensory responses (eg, exquisite sensitivity to noises, food odors or tastes, or clothing textures) Pragmatic deficits (eg, extremely concrete use of language, difficulty recognizing irony or jokes) Autism (autistic disorder) Onset usually before age 3 yr Impaired social interaction and communication Repetitive stereotyped behavior Some degree of intellectual disability in many cases Severe regression of language and sociability occurring between 18 and 24 mo in about 25% of cases Childhood disintegrative disorder After 2 yr of normal growth, marked regression in at least 2 of the following: Social skills Language Bladder and bowel control Motor skills Eventually may become more severe than is typical in autism Other behaviors that may mimic autism or childhood schizophrenia Pervasive developmental disorder not otherwise specified Does not meet criteria for any of other subtypes yet includes a wide range of cognitive and behavioral problems and impairment in social interactions Generally less severe than autism Rett syndrome Affects development after initial 6-mo period of normal development Deceleration of head growth Severe intellectual disability Impaired social interaction Loss of speech (if any was present) and purposeful use of hands (results in hand-wringing stereotypy) Seizures Autistic features Ataxia Affects predominantly girls (caused by mutation in MECP2 gene on Xq28)

Etiology

The specific cause in most cases of ASD remains elusive. However, some cases have occurred with congenital rubella syndrome, cytomegalic inclusion disease, phenylketonuria, or fragile X syndrome.

Strong evidence supports a genetic component. For parents of one child with an ASD, risk of having a subsequent child with an ASD is 50 to 100 times greater. The concordance rate of autism is high in monozygotic twins. Research on families has suggested several potential target gene areas, including those related to neurotransmitter receptors (serotonin and gamma-aminobutyric acid [GABA]) and CNS structural control (HOX genes). Environmental causes have been suspected but are unproved. There is strong evidence that vaccinations do not cause autism; however, many in the public still hold this belief.

Abnormalities of brain structure and function probably underlie much of the pathogenesis of autism. Some children with autism have enlarged ventricles, some have hypoplasia of the cerebellar vermis, and others have abnormalities of brain stem nuclei.

Symptoms and Signs

Classic autistic disorder usually manifests in the first year of life and almost always by age 3. The disorder is characterized by

• Atypical interaction (ie, lack of attachment, inability to cuddle or to form reciprocal relationships, avoidance of eye gaze)
• Insistence on sameness (ie, resistance to change, performance of rituals, intense attachment to familiar objects, stereotyped and repetitive behavior)
• Speech and language problems (ranging from total muteness to delayed onset of speech to markedly idiosyncratic use of language)
• Uneven intellectual performance

Some affected children injure themselves. About 25% of affected children experience a documented loss of previously acquired skills.

All children with ASD have similar problems with interaction, behavior, and communication; however, the severity of the problems varies widely. Nevertheless, some characteristic features often point to the specific diagnosis (see Table 2: Learning and Developmental Disorders: Autism Spectrum Disorders). Children with Asperger syndrome generally have better intellectual performance than children with classic autistic disorder. They also lack the language delays typical of children with classic autistic disorder; however, they still have detectable abnormalities of pragmatic (social) language, such as literal interpretation of idiomatic speech and difficulty understanding jokes. Children with childhood disintegrative disorder develop normally until about age 2, and then their skills deteriorate.

Current theory holds that a fundamental problem in ASD is mind blindness, the inability to imagine what another person might be thinking. This difficulty is thought to result in interaction abnormalities that, in turn, lead to abnormal language development. One of the earliest and most sensitive markers for autism is a 1-yr-old child's inability to point communicatively at objects. It is theorized that the child cannot imagine that another person would understand what was being indicated; instead, the child indicates wants only by physically touching the desired object or using the adult's hand as a tool.

Nonfocal neurologic findings include poorly coordinated gait and stereotyped motor movements. Seizures occur in 20 to 40% of these children (particularly those with an IQ < 50).

Diagnosis

• Clinical evaluation

Diagnosis is made clinically and usually requires evidence of impairment of social interaction and communication and presence of restricted, repetitive, stereotyped behaviors or interests. Screening tests include the Social Communication Questionnaire and the Modified Checklist for Autism in Toddlers (M-CHAT). M-CHAT is available online.See also the American Academy of Neurology's Practice Parameter: Screening and Diagnosis of Autism and the American Academy of Pediatrics' Identification and Evaluation of Children with Autism Spectrum Disorders. Formal standard diagnostic tests such as the Autism Diagnostic Observation Schedule (ADOS), based on criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision (DSM-IV-TR), are usually given by psychologists or developmental-behavioral pediatricians. Children with ASD are difficult to test; they usually do better on performance items than verbal items in IQ tests and may show instances of age-appropriate performance despite cognitive limitation in most areas. Nonetheless, an IQ test given by an experienced examiner often can provide a useful predictor of outcome.

Treatment

• Behavioral therapy
• Speech and language therapy
• Sometimes physical and occupational therapy
• Drug therapy

Treatment is usually multidisciplinary, and recent studies show measurable benefits from intensive, behaviorally based approaches that encourage interaction and meaningful communication. Psychologists and educators typically focus on behavioral analysis and then match behavioral management strategies to specific behavioral problems at home and at school. See also the American Academy of Pediatrics' Management of Children with Autism Spectrum Disorders.

Speech and language therapy should begin early and use a range of media, including signing, picture exchange, and augmentative communication devices such as those that generate speech based on symbols children select on a tablet or other handheld device, and speech. Physical and occupational therapists plan and implement strategies to help affected children compensate for specific deficits in motor function and motor planning.

There is evidence that atypical antipsychotic drugs (eg, risperidone, aripiprazole) help relieve behavioral problems, such as ritualistic, self-injurious, and aggressive behaviors. Other drugs are sometimes used for control of specific symptoms, including SSRIs for ritualistic behaviors, mood stabilizers (eg, valproate) for self-injury and outburst behaviors, and stimulants and other attention-deficit/hyperactivity disorder (ADHD) drugs for inattention, impulsivity, and hyperactivity.

Dietary interventions, including some vitamin supplements and a gluten-free and casein-free diet, are not helpful enough to be recommended; however, many families choose to use them. Other complementary and investigational approaches to therapy (eg, facilitated communication, chelation therapy, auditory integration training, and hyperbaric O₂ therapy) have not yet shown efficacy.

Key Points

• Children have some combination of impaired social interaction and communication, repetitive and stereotyped patterns of behavior, and uneven intellectual development often with intellectual disability.
• Cause is usually unknown, but there appears to be a genetic component; vaccines are not causative.
• Screening tests include the Social Communication Questionnaire and the Modified Checklist for Autism in Toddlers (M-CHAT)
• Formal diagnostic testing is usually done by psychologists or developmental-behavioral pediatricians.
• Treatment is usually multidisciplinary, using intensive, behaviorally based approaches that encourage interaction and communication.
• Drugs (eg, atypical antipsychotics) may help severe behavioral disturbances (eg, self-injury, aggression).

Last full review/revision March 2013 by Stephen Brian Sulkes, MD