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Autism spectrum disorders are disorders in which young children cannot develop normal social relationships, use language abnormally or not at all, behave in compulsive and ritualistic ways, and may fail to develop normal intelligence.
Autism is one of several related disorders of brain development. These disorders, known as autism spectrum disorders (ASD) or pervasive developmental disorders, occur in 1 of 150 children. Classic autism is the most common of these disorders. Asperger's syndrome, Rett syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS) are the other ASD. Symptoms of ASD may appear in the first 2 years of life, but in milder forms symptoms may not be detected until school age. These disorders are 2 to 4 times more common among boys than among girls. Autism is different from intellectual disability (previously called mental retardation), although many children with autism have both.
The specific causes of ASD are not fully understood, although they are clearly biologically determined. Several chromosomal abnormalities, such as fragile X syndrome, contribute to the development of autism. Prenatal infections, for example, viral infections such as rubella or cytomegalovirus, may also play a role. It is clear, however, that ASDs are not caused by poor parenting, adverse childhood conditions, or vaccination.
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| Comparing Autism Spectrum Disorders |
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Disorder
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Effects
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Description
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Asperger's syndrome
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Generally, language and cognitive skills are better than those in children with autism.
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Children are socially isolated and often viewed as odd or eccentric.
Children typically have repetitive patterns of behavior.
They usually have specific, narrow, and obsessive interests and activities.
Sensation may be unusual. For example, children may be very sensitive to noises, food odors or tastes, or clothing textures.
Children tend to use and understand language concretely and literally. Thus, they have difficulty recognizing irony or jokes.
Movements become clumsy.
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Autism (autistic disorder)
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It begins before age 3 years.
Intellectual disability is impaired to some degree in many children, and severe regression of language and sociability occurs between age 18 and 24 months in about 25%.
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Social interaction and communication are markedly impaired.
Children may not make eye contact or be able to understand tone of voice or facial expressions.
Children typically have repetitive stereotyped patterns of behavior.
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Childhood disintegrative disorder
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After 2 years of normal growth, a marked regression occurs in at least two of the following:
Eventually, symptoms may become more severe than is typical in autism.
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Some characteristics may resemble those of autism (such as repetitive stereotyped behavior) or those of childhood schizophrenia (such as lack of response to emotional situations).
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Other pervasive developmental disorders
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Symptoms are less severe than those of autism.
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These disorders include a wide range of intellectual, behavioral, and social problems that do not match the criteria needed to diagnose a specific disorder. Thus, these disorders are called pervasive developmental disorders not otherwise specified (PDD-NOS).
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Rett syndrome
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It begins after 6 months of normal development and causes severe intellectual disability.
It is caused by a gene mutation and affects girls almost exclusively.
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The brain and head do not grow as quickly as expected.
Social interaction is impaired.
Children lose the ability to speak.
They become unable to use their hands purposefully and typically wring them compulsively.
Seizures may occur, and coordination is lost.
Some characteristics (for example, toe walking and body rocking) may resemble those of autism.
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Symptoms
Children with ASD develop symptoms in at least 3 of the following areas:
Symptoms range from mild to severe and often keep children from functioning independently in school or society. In addition, about 20 to 40% of children with autism, particularly those with an intelligence quotient (IQ) less than 50, develop seizures before reaching adolescence. In about 25% of affected children, a regression in development occurs around the time of diagnosis and may be the initial indicator of a disorder.
Social Relationships:
Often, infants with ASD do not cuddle and avoid eye contact. Although some affected infants become upset when separated from their parents, they may not turn to parents for security as do other children. Older children often prefer to play by themselves and do not form close personal relationships, particularly outside of the family. When interacting with other children, they may not use eye contact and facial expressions to establish social contact, and they are not able to interpret the moods and expressions of others.
Language:
About 50% of children with classic autism never learn to speak. Those who learn do so much later than normal and use words in an unusual way. They often repeat words spoken to them (echolalia) or reverse the normal use of pronouns, particularly using you instead of I or me when referring to themselves. These children rarely have an interactive dialogue with others. They also often speak with an unusual rhythm and pitch.
Behavior:
Children with ASD are very resistant to changes, such as new food, toys, furniture arrangement, and clothing. They often become excessively attached to particular inanimate objects. They often repeat certain acts, such as rocking, hand flapping, or spinning objects in a repetitive manner. Some may injure themselves through repetitive behaviors such as head banging or biting themselves.
Intelligence:
About 70% of children with ASD have some degree of intellectual disability (an IQ less than 70). Their performance is uneven. They usually do better on tests of motor and spatial skills than on verbal tests. Some children with autism have idiosyncratic or splinter skills, such as the ability to carry out complex mental arithmetic or advanced musical skills. Unfortunately, such children often cannot use these skills in a productive or socially interactive way.
Diagnosis
The diagnosis is made by close observation of the child in a playroom setting and careful questioning of parents and teachers. Standardized tests, such as the Gilliam Autism Rating Scale or the more extensive Autism Diagnostic Observational Schedule, may help the evaluation. In addition to giving standardized tests, doctors should do certain tests to look for underlying treatable or inherited medical disorders, such as hereditary metabolic disorders (see Hereditary Metabolic Disorders: Overview of Hereditary Metabolic Disorders) and fragile X syndrome (see Chromosomal and Genetic Abnormalities: Fragile X Syndrome).
Prognosis and Treatment
The symptoms of autism generally persist throughout life. The prognosis is strongly influenced by how much usable language the child has acquired by age 7. Children with autism who have lower measured intelligence—for example, those who score below 50 on standard IQ tests—are likely to need more intensive support as adults.
Children with ASD often benefit from intensive behavioral modification techniques. Children with higher IQs are helped by therapy aimed at developing social skills. Individualized special education is crucial and often includes speech, occupational, physical, and behavioral therapy within a program equipped to manage children with autism.
Drug therapy cannot change the underlying disorder. However, the selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, paroxetine, and fluvoxamine, are often effective in reducing ritualistic behaviors of children with autism. Antipsychotic drugs, such as risperidone, may be used to reduce self-injurious behavior, although the risk of side effects (such as weight gain and movement disorders) must be considered.
Although some parents try special diets, gastrointestinal therapies, or immunologic therapies, currently there is no good evidence that any of these therapies helps children with autism.
Asperger's Syndrome and Pervasive Developmental Disorder Not Otherwise Specified
These autism spectrum disorders are closely related to classic autism but are less severe.
Children with Asperger's syndrome have impaired social interactions similar to those of children with autism, as well as stereotyped or repetitive behaviors and mannerisms and nonfunctional rituals. Their speech and language skills are normal, but they often have weakness in pragmatic (social) language. They have normal intelligence but also often have intense interests in narrow topics to the exclusion of other developmentally appropriate pursuits.
Children who have significantly impaired social interactions or stereotyped behaviors without all of the features of autism or Asperger's syndrome are considered to have pervasive developmental disorder not otherwise specified (abbreviated as PDD-NOS). Children with Asperger's syndrome or PDD-NOS tend to function at a higher level than children with classic autism and may be able to function independently. Children with Asperger's syndrome often respond well to psychotherapy.
Rett Syndrome
Rett syndrome is a rare genetic disorder occurring almost only in girls that causes impaired social interactions, loss of language skills, and repetitive hand movements.
Girls with Rett syndrome appear to develop normally until some time between the age of 5 months and 4 years. When the disorder begins, head growth slows and language and social skills deteriorate. Typically, girls display repetitive hand motions resembling washing or wringing. Purposeful hand movements are lost, walking is impaired, and trunk movements are clumsy. Intellectual disability develops and is usually severe.
Slight spontaneous improvements in social interaction may occur in late childhood and early adolescence, but the language and behavior problems progress. Most girls with Rett syndrome need full-time support and specialized educational programs. There is no cure.
Childhood Disintegrative Disorder
In childhood disintegrative disorder, apparently normal children begin to act younger (regress) after age 3.
In most children, physical and mental development occurs in spurts. It is common for children to take a step backward. For example, toilet-trained children occasionally wet themselves. Childhood disintegrative disorder, however, is a rare serious disorder in which children older than age 3 stop developing normally and regress to a much lower level of functioning, typically following a serious illness, such as an infection of the brain and nervous system.
Typical children with childhood disintegrative disorder develop normally until age 3 or 4, learning speech, becoming toilet trained, and displaying appropriate social behavior. Then, after a period of a few weeks or months during which time affected children are irritable and moody, they undergo obvious regression. Children may lose previously acquired language, motor, or social skills and may no longer have control over bladder or bowel function. In addition, children develop difficulties in social interaction and begin performing repetitive behaviors similar to those that occur in children with autism. Quite often children gradually deteriorate to a level of severe intellectual disability. Doctors make the diagnosis based on the symptoms and search for an underlying disorder. In cases of marked regression, a neurologic evaluation to look for treatable causes is essential.
Childhood disintegrative disorder cannot be specifically treated or cured, and most children, particularly those with more severe disability, need lifelong support.
Last full review/revision February 2009 by Stephen Brian Sulkes, MD
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