Autism Spectrum Disorders (Pervasive Developmental Disorders)
Pervasive Developmental Disorders
description
Transcript of Pervasive Developmental Disorders
Pervasive Developmental Disorders
Pervasive developmental disorders include several that are characterized by impaired reciprocal
social interactions, aberrant language development, and restricted behavioral repertoire.
Pervasive developmental disorders typically emerge in young children before the age of 3 years,
and parents often become concerned about a child by 18 months as language development does
not occur as expected. In about 25 percent of cases, some language develops and is subsequently
lost. Some children with pervasive developmental disorders are not identified with problems
until school age, because they make relatively few demands and have minimal conflicts with
others owing to their infrequent social engagement. Children with pervasive developmental
disorders often exhibit idiosyncratic intense interest in a narrow range of activities, resist change,
and are not appropriately responsive to the social environment. These disorders affect multiple
areas of development, are manifested early in life, and cause persistent dysfunction. Autistic
disorder, the best known of these disorders, is characterized by sustained impairment in
comprehending and responding to social cues, aberrant language development and usage, and
restricted, stereotypical behavioral patterns. According to the text revision of the 4th edition of
Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), to meet criteria for
autistic behavior, abnormal functioning in at least one of the above areas must be present by age
3 years. More than two thirds of children with autistic disorder have mental retardation, although
it is not required for the diagnosis.
The DSM-IV-TR includes five pervasive developmental disorders: autistic disorder, Rett's
disorder, childhood disintegrative disorder, Asperger's disorder, and pervasive developmental
disorder not otherwise specified. Rett's disorder appears to occur exclusively in girls; it is
characterized by normal development for at least 6 months, stereotyped hand movements, a loss
of purposeful motions, diminishing social engagement, poor coordination, and decreasing
language use. In childhood disintegrative disorder, development progresses normally for the first
2 years, after which the child shows a loss of previously acquired skills in two or more of the
following areas: language use, social responsiveness, play, motor skills, and bladder or bowel
control. Asperger's disorder is a condition in which the child is markedly impaired in social
relatedness and shows repetitive and stereotyped patterns of behavior without a delay in
language development. In Asperger's disorder, a child's cognitive abilities and adaptive skills are
normal. A recent survey revealed that the average age of diagnosis for children with pervasive
developmental disorders was 3.1 years for children with autistic disorder, 3.9 years for pervasive
developmental disorder not otherwise specified, and 7.2 years for Asperger's disorder. Children
with severe language deficits received a diagnosis an average of a year earlier than other
children. Children with behaviors such as hand-flapping, toe-walking, and odd play were
identified with disorders at a younger age.
Autistic Disorder
Autistic disorder (historically called early infantile autism, childhood autism, or Kanner's autism)
is characterized by symptoms from each of the following three categories: qualitative impairment
in social interaction, impairment in communication, and restricted repetitive and stereotyped
patterns of behavior or interests.
History
As early as 1867, Henry Maudsley, a psychiatrist, noted a group of very young children with
severe mental disorders who had marked deviation, delay, and distortion in development. In that
era, most serious disturbance in young children was believed to fall within the category of
psychoses. In 1943 Leo Kanner, in his classic paper “Autistic Disturbances of Affective
Contact,†coined the term infantile � autism and provided a clear, comprehensive account of the
early childhood syndrome. He described children who exhibited extreme autistic aloneness;
failure to assume an anticipatory posture; delayed or deviant language development with
echolalia and pronominal reversal (using you for I); monotonous repetitions of noises or verbal
utterances; excellent rote memory; limited range of spontaneous activities, stereotypies, and
mannerisms; anxiously obsessive desire for the maintenance of sameness and dread of change;
poor eye contact; abnormal relationships with persons; and a preference for pictures and
inanimate objects. Kanner suspected that the syndrome was more frequent than it seemed and
suggested that some children with this disorder had been misclassified as mentally retarded or
schizophrenic. Before 1980, children with pervasive developmental disorders were generally
diagnosed with childhood schizophrenia. Over time, it became evident that autistic disorder and
schizophrenia were two distinct psychiatric entities. In some cases, however, a child with autistic
disorder may develop a comorbid schizophrenic disorder later in childhood.
Epidemiology
Prevalence
Autistic disorder is believed to occur at a rate of about 8 cases per 10,000 children (0.08 percent).
Multiple epidemiologic surveys mainly in Europe have resulted in variable
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rates of autistic disorder ranging from 2 to 30 cases per 10,000. By definition, the onset of
autistic disorder is before the age of 3 years, although in some cases, it is not recognized until a
child is much older.
Sex Distribution
Autistic disorder is four to five times more frequent in boys than in girls. Girls with autistic
disorder are more likely to have more severe mental retardation.
Socioeconomic Status
Early studies suggested that a high socioeconomic status was more common in families with
autistic children; however, these findings were probably based on referral bias. Over the past 25
years, no epidemiological studies have demonstrated an association between autistic disorder and
any socioeconomic status.
Etiology and Pathogenesis
Genetic Factors
Current evidence supports a genetic basis for the development of autistic disorder in most cases,
with a contribution of up to four or five genes. Family studies have demonstrated a 50 to 200
times increase in the rate of autism in siblings of an index child with autistic disorder.
Additionally, even when not affected with autism, siblings are at increased risk for a variety of
developmental disorders often related to communication and social skills. These difficulties in
the nonautistic relatives of people with autistic disorder are also known by researchers as the
“broad phenotype.†The specific modes of inheritance are not yet clear. Hypotheses include �genetic inheritance of a more general predisposition to developmental difficulties and specific
genetic etiology of autistic disorder.
Current research has revealed promising leads on candidate genes likely to underlie the
development of autistic disorder. Linkage analyses have demonstrated that regions of
chromosomes 7, 2, 4, 15, and 19 are likely to contribute to the genetic basis of autism. It now
appears that multiple genes are involved in the development of autism. Researchers hypothesize
that some genetic forms of autism may be identified in the near future.
The concordance rate of autistic disorder in the two largest twin studies was 36 percent in
monozygotic pairs versus 0 percent in dizygotic pairs in one study and about 96 percent in
monozygotic pairs versus about 27 percent in dizygotic pairs in the second study. High rates of
cognitive difficulties, even in the nonautistic twin in monozygotic twins with perinatal
complications, suggest that contributions of perinatal insult along with genetic vulnerability may
lead to autistic disorder.
Fragile X syndrome, a genetic disorder in which a portion of the X chromosome fractures,
appears to be associated with autistic disorder. Approximately 1 percent of children with autistic
disorder also have fragile X syndrome. Children with fragile X syndrome tend to show gross
motor and fine motor difficulties as well as relatively poorer expressive language compared with
children with autism without fragile X syndrome. Tuberous sclerosis, a genetic disorder
characterized by multiple benign tumors, with autosomal dominant transmission is found with
greater frequency among children with autistic disorder. Up to 2 percent of children with autistic
disorder may also have tuberous sclerosis.
Recently, researchers screened the DNA of more than 150 pairs of siblings with autism. They
found extremely strong evidence that two regions on chromosomes 2 and 7 contain genes
involved with autism. Likely locations for autism-related genes were also found on
chromosomes 16 and 17, although the strength of the correlation was somewhat weaker.
Historically, Kanner, in 1943, described 11 cases of developmentally disordered people and
hypothesized that their autistic features were caused by emotionally unresponsive
“refrigerator†mothers, but no validity exists to this hypothesis. On the other hand, much �evidence supports a biological substrate for this disorder.
Biological Factors
The high rate of mental retardation among children with autistic disorder and the higher-than-
expected rates of seizure disorders further support the biological basis for autistic disorder.
Approximately 70 percent of children with autistic disorder have mental retardation. About one
third of these children have mild to moderate mental retardation, and close to half of these
children are severely or profoundly mentally retarded. Children with autistic disorder and mental
retardation typically show more marked deficits in abstract reasoning, social understanding, and
verbal tasks than in performance tasks, such as block design and digit recall, in which details can
be remembered without reference to the “gestalt†meaning.�
Of persons with autism, 4 to 32 percent have grand mal seizures at some time, and about 20 to 25
percent show ventricular enlargement on computed tomography (CT) scans. Various
electroencephalogram (EEG) abnormalities are found in 10 to 83 percent of autistic children, and
although no EEG finding is specific to autistic disorder, there is some indication of failed
cerebral lateralization. Recently, one magnetic resonance imaging (MRI) study revealed
hypoplasia of cerebellar vermal lobules VI and VII, and another MRI study revealed cortical
abnormalities, particularly polymicrogyria, in some autistic patients. Those abnormalities may
reflect abnormal cell migrations in the first 6 months of gestation. An autopsy study revealed
fewer Purkinje's cells, and another study found increased diffuse cortical metabolism during
positron emission tomography (PET) scanning.
Autistic disorder is also associated with neurological conditions, notably congenital rubella,
phenylketonuria (PKU), and tuberous sclerosis. Autistic children have higher than expected
histories of perinatal complications compared with the general population and also compared
with children with other psychiatric disorders. The finding that autistic children have
significantly more minor congenital physical anomalies than expected suggests abnormal
development within the first trimester of pregnancy.
Immunological Factors
Several reports have suggested that immunological incompatibility (i.e., maternal antibodies
directed at the fetus) may contribute to autistic disorder. The lymphocytes of some autistic
children react with maternal antibodies, which raises the possibility that embryonic neural or
extraembryonic tissues may be damaged during gestation.
Perinatal Factors
A higher-than-expected incidence of perinatal complications seems to occur in infants who are
later diagnosed with autistic disorder. Maternal bleeding after the first trimester and meconium in
the amniotic fluid have been reported in the histories of autistic children more often than in the
general population. In the neonatal period, autistic children have a high incidence of respiratory
distress syndrome and neonatal anemia.
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Males with autism, as a group, have been found to be the products of longer gestational age and
were heavier at birth than babies in the general population. Females with autism are more likely
to be the product of postterm pregnancies than babies in the general population.
Neuroanatomical Factors
The neuroanatomical basis of autism remains unknown; however, recent evidence suggests that
enlargement of gray and white matter cerebral volumes, but not cerebellar volumes, are present
in children with autistic disorder at 2 years of age. Head circumference appears normal at birth,
and the increased rate of head circumference growth appears to emerge at about 12 months of
age. Previous MRI studies comparing autistic subjects and normal controls revealed total brain
volume was larger in those with autism, although autistic children with severe mental retardation
generally have smaller heads. The greatest average percentage increase in size occurred in the
occipital lobe, parietal lobe, and temporal lobe. No differences were found in the frontal lobes.
Specific origins of this enlargement are unknown. The increased volume can arise from three
different possible mechanisms: increased neurogenesis, decreased neuronal death, and increased
production of nonneuronal brain tissue, such as glial cells or blood vessels. Brain enlargement
has been suggested as a possible biological marker for autistic disorder.
The temporal lobe is believed to be one of the critical areas of brain abnormality in autistic
disorder. This suggestion is based on reports of autistic-like syndromes in some persons with
temporal lobe damage. When the temporal region of animals is damaged, normal social behavior
is lost, and restlessness, repetitive motor behavior, and a limited behavioral repertoire are seen.
Some brains of autistic individuals exhibit a decrease in cerebellar Purkinje's cells, which is
believed to account potentially for abnormalities of attention, arousal, and sensory processes.
Interesting reports of differences between male and female brains are hypothesized to have
possible implications for understanding autism insofar as the traits of “empathy†and �“systemizing.†Empathizing, the capacity to predict and respond to feelings and behavior of �others by inferring their emotional states, is a stronger trait in females than in males at a
population level. Males, on the other hand, at a population level, are stronger at systemizing, that
is, inferring rules that govern “cause and effect†relationships of behaviors. People with �pervasive developmental disorders are characterized by deficits in empathizing, and those with
high intellectual capacity have been reported to have relative strengths in rule bound thinking.
Biochemical Factors
A number of studies in the last few decades have demonstrated that about one third of patients
with autistic disorder have high plasma serotonin concentrations. This finding, however, is not
specific to autistic disorder, and persons with mental retardation without autistic disorder also
display this trait. Several studies have reported that autistic individuals without mental
retardation have a high incidence of hyperserotonemia. In some autistic children, a high
concentration of homovanillic acid (the major dopamine metabolite) in cerebrospinal fluid (CSF)
is associated with increased withdrawal and stereotypes. Some evidence indicates that symptom
severity decreases as the ratio of 5-hydroxyindoleacetic acid (5-HIAA, metabolite of serotonin)
to homovanillic acid in CSF increases. The 5-HIAA concentration in CSF may be inversely
proportional to blood serotonin concentrations, which are increased in one third of autistic
disorder patients, a nonspecific finding that also occurs in mentally retarded persons.
Psychosocial and Family Factors
Studies comparing parents of autistic children with parents of normal children have shown no
significant differences in child-rearing skills.
Children with autistic disorder, as children with other disorders, can respond with exacerbated
symptoms to psychosocial stressors, including family discord, the birth of a new sibling, or a
family move. Some children with autistic disorder may be excruciatingly sensitive to even small
changes in their families and immediate environment.
Diagnosis and Clinical Features
The DSM-IV-TR diagnostic criteria for autistic disorder are given in Table 42-1.
Physical Characteristics
On first glance, children with autistic disorder do not show any physical signs indicating the
disorder. These children do have high rates of minor physical anomalies, such as ear
malformations, and others that may reflect abnormalities in fetal development of those organs
along with parts of the brain.
A greater than expected number of autistic children do not show lateralization and remain
ambidextrous at an age when cerebral dominance is established in most children. Autistic
children also have a higher incidence of abnormal dermatoglyphics (e.g., fingerprints) than those
in the general population. This finding may suggest a disturbance in neuroectodermal
development.
Behavioral Characteristics
Qualitative Impairments In Social Interaction
Autistic children do not exhibit the expected level of subtle reciprocal social skills that
demonstrate relatedness to parents and peers. As infants, many lack a social smile and
anticipatory posture for being picked up as an adult approaches. Less frequent or poor eye
contact is common. The social development of autistic children is characterized by impaired, but
not usually totally absent, attachment behavior. Autistic children often do not acknowledge or
differentiate the most important persons in their lives—parents, siblings, and teachers—and
may show extreme anxiety when their usual routine is disrupted, but they may not react overtly
to being left with a stranger. When autistic children have reached school age, their withdrawal
may have diminished and be less obvious, particularly in higher-functioning children. A notable
deficit is seen in ability to play with peers and to make friends; their social behavior is awkward
and may be inappropriate. Cognitively, children with autistic disorder are more skilled in visual-
spatial tasks than in tasks requiring skill in verbal reasoning.
One description of the cognitive style of children with autism is that they cannot infer the
feelings or mental state of others around them. That is, they cannot make attributions about the
motivation or intentions of others and, thus, cannot develop empathy. This lack of a “theory
of mind†leaves them unable to �P.1194
interpret the social behavior of others and leads to a lack of social reciprocation.
Table 42-1 DSM-IV-TR Diagnostic Criteria for Autistic Disorder
A. A total of six (or more) items from (1), (2), and (3), with at least two from (1), and one
each from (2) and (3):
1. qualitative impairment in social interaction, as manifested by at least two of the
following:
a. marked impairment in the use of multiple nonverbal behaviors such as
eye-to-eye gaze, facial expression, body postures, and gestures to regulate
social interaction
b. failure to develop peer relationships appropriate to developmental level
c. a lack of spontaneous seeking to share enjoyment, interests, or
achievements with other people (e.g., by a lack of showing, bringing, or
pointing out objects of interest)
d. lack of social or emotional reciprocity
2. qualitative impairments in communication as manifested by at least one of the
following:
a. delay in, or total lack of, the development of spoken language (not
accompanied by an attempt to compensate through alternative modes of
communication such as gesture or mime)
b. in individuals with adequate speech, marked impairment in the ability to
initiate or sustain a conversation with others
c. stereotyped and repetitive use of language or idiosyncratic language
d. lack of varied, spontaneous make-believe play or social imitative play
appropriate to developmental level
3. restricted repetitive and stereotyped patterns of behavior, interests, and activities,
as manifested by at least one of the following:
a. encompassing preoccupation with one or more stereotyped and restricted
patterns of interest that is abnormal either in intensity or focus
b. apparently inflexible adherence to specific, nonfunctional routines or
rituals
c. stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping
or twisting, or complex whole-body movements)
d. persistent preoccupation with parts of objects
B. Delays or abnormal functioning in at least one of the following areas, with onset prior to
age 3 years: (1) social interaction, (2) language as used in social communication, or (3)
symbolic or imaginative play.
C. The disturbance is not better accounted for by Rett's disorder or childhood disintegrative
disorder.
(From American Psychiatric Association. Diagnostic and Statistical Manual of Mental
Disorders. 4th ed. Text rev. Washington, DC: American Psychiatric Association; copyright
2000, with permission.)
In late adolescence, autistic persons often desire friendships, but their difficulties in responding
to another's interests, emotions, and feelings are major obstacles in developing them. They are
often shunned by peers and behave in awkward ways that alienate them from others. Autistic
adolescents and adults experience sexual feelings, but their lack of social competence and skills
prevents many of them from developing sexual relationships.
Disturbances of Communication and Language
Deficits in language development and difficulty using language to communicate ideas are among
the principal criteria for diagnosing autistic disorder. Autistic children are not simply reluctant to
speak, and their speech abnormalities do not result from lack of motivation. Language deviance,
as much as language delay, is characteristic of autistic disorder. In contrast to normal and
mentally retarded children, autistic children have significant difficulty putting meaningful
sentences together even when they have large vocabularies. When children with autistic disorder
do learn to converse fluently, their conversations may impart information without providing a
sense of acknowledging how the other person is responding. In children with autism and
nonautistic children with language disorders, nonverbal communication skills may also be
impaired when significant difficulty with expressive language exists.
In the first year of life, an autistic child's pattern of babbling may be minimal or abnormal. Some
children emit noises—clicks, sounds, screeches, and nonsense syllables—in a stereotyped
fashion, without a seeming intent of communication. Unlike normal young children, who
generally have better receptive language skills than expressive ones, verbal autistic children may
say more than they understand. Words and even entire sentences may drop in and out of a child's
vocabulary. It is not atypical for a child with autistic disorder to use a word once and then not use
it again for a week, a month, or years. Children with autistic disorder typically exhibit speech
that contains echolalia, both immediate and delayed, or stereotyped phrases that seem out of
context. These language patterns are frequently associated with pronoun reversals. A child with
autistic disorder might say, “You want the toy†when she means that she wants it. �Difficulties in articulation are also common. Many children with autistic disorder use peculiar
voice quality and rhythm. About 50 percent of autistic children never develop useful speech.
Some of the brightest children show a particular fascination with letters and numbers. Children
with autistic disorder sometimes excel in certain tasks or have special abilities; for example, a
child may learn to read fluently at preschool age (hyperlexia), often astonishingly well. Very
young autistic children who can read many words, however, have little comprehension of the
words read.
Stereotyped Behavior
In the first years of an autistic child's life, much of the expected spontaneous exploratory play is
absent. Toys and objects are often manipulated in a ritualistic manner, with few symbolic
features. Autistic children generally do not show imitative play or use abstract pantomime. The
activities and play of these children are often rigid, repetitive, and monotonous. Ritualistic and
compulsive phenomena are common in early and middle childhood. Children often spin, bang,
and line up objects and may exhibit an attachment to a particular inanimate object. Many autistic
children, especially those who are severely mentally retarded, exhibit movement abnormalities.
Stereotypies, mannerisms, and grimacing are most frequent when a child is left alone and may
decrease in a structured situation. Autistic children are generally resistant to transition and
change. Moving to a new house, moving furniture in a room, or a change, such as having
breakfast before a bath when the reverse was the routine, may evoke panic, fear, or temper
tantrums.
Instability of Mood and Affect
Some children with autistic disorder exhibit sudden mood changes, with bursts of laughing or
crying without an obvious reason. It is difficult to learn more about these episodes if the child
cannot express the thoughts related to the affect.
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Response to Sensory Stimuli
Autistic children have been observed to overrespond to some stimuli and underrespond to other
sensory stimuli (e.g., to sound and pain). It is not uncommon for a child with autistic disorder to
appear deaf, at times showing little response to a normal speaking voice; on the other hand, the
same child may show intent interest in the sound of a wristwatch. Some children with autistic
disorder have a heightened pain threshold or an altered response to pain. Indeed, some autistic
children do not respond to an injury by crying or seeking comfort. Many autistic children
reportedly enjoy music. They frequently hum a tune or sing a song or commercial jingle before
saying words or using speech. Some particularly enjoy vestibular stimulation—spinning,
swinging, and up-and-down movements.
Associated Behavioral Symptoms
Hyperkinesis is a common behavior problem in young autistic children. Hypokinesis is less
frequent; when present, it often alternates with hyperactivity. Aggression and temper tantrums
are observed, often prompted by change or demands. Self-injurious behavior includes head
banging, biting, scratching, and hair pulling. Short attention span, poor ability to focus on a task,
insomnia, feeding and eating problems, and enuresis are also common among children with
autism.
Associated Physical Illness
Young children with autistic disorder have been reported to have a higher-than-expected
incidence of upper respiratory infections and other minor infections. Gastrointestinal symptoms
commonly found among children with autistic disorder include excessive burping, constipation,
and loose bowel movements. Also seen is an increased incidence of febrile seizures in children
with autistic disorder. Some autistic children do not show temperature elevations with minor
infectious illnesses and may not show the typical malaise of ill children. In some children,
behavior problems and relatedness seem to improve noticeably during a minor illness, and in
some, such changes are a clue to physical illness.
A standardized instrument that can be very helpful in eliciting comprehensive information
regarding developmental disorders is the Autism Diagnostic Observation Schedule-Generic
(ADOS-G).
John was the second of two children born to middle-class parents after normal pregnancy, labor,
and delivery. As an infant, John appeared undemanding and relatively placid; motor
development proceeded appropriately, but language development was delayed. Although his
parents indicated that they were first concerned about his development when he was 18 months
of age and still not speaking, in retrospect, they noted that, in comparison to their previous child,
he had seemed relatively uninterested in social interaction and the social games of infancy.
Stranger anxiety had never really developed, and John did not exhibit differential attachment
behaviors toward his parents. Their pediatrician initially reassured John's parents that he was a
“late talker,†but they continued to be concerned. Although John seemed to respond to some �unusual sounds, the pediatrician obtained a hearing test when John was 24 months old. Levels of
hearing appeared adequate for development of speech, and John was referred for developmental
evaluation. At 24 months, motor skills were age appropriate, and John exhibited some nonverbal
problem-solving skills close to age level. His language and social development, however, were
severely delayed, and he was noted to be resistant to changes in routine and unusually sensitive
to aspects of the inanimate environment. His play skills were quite limited, and he used play
materials in unusual and idiosyncratic ways. His older sister had a history of some learning
difficulties, but the family history was otherwise negative. A comprehensive medical evaluation
revealed a normal EEG and CT scan; genetic screening and chromosome analysis were normal
as well.
John was enrolled in a special education program, in which he gradually began to speak. His
speech was characterized by echolalia, extreme literalness, a monotonic voice quality, and
pronoun reversal. He rarely used language in interaction and remained quite isolated. By school
age, John had developed some evidence of differential attachments to family members; he also
had developed a number of self-stimulatory behaviors and engaged in occasional periods of head
banging. Extreme sensitivity to change continued. Intelligence testing revealed marked scatter,
with a full-scale intelligence quotient (IQ) in the moderately retarded range. As an adolescent,
John's behavioral functioning deteriorated, and he developed a seizure disorder. Now an adult, he
lives in a group home and attends a sheltered workshop. He has a rather passive interactional
style but exhibits occasional outbursts of aggression and self-abuse. (Courtesy of Fred Volkmar,
M.D.)
Intellectual Functioning
About 70 to 75 percent of children with autistic disorder function in the mentally retarded range
of intellectual function. About 30 percent of children function in the mild to moderate range, and
about 45 to 50 percent are severely to profoundly mentally retarded. Epidemiological and clinical
studies show that the risk for autistic disorder increases as the IQ decreases. About one fifth of
all autistic children have a normal, nonverbal intelligence. The IQ scores of autistic children tend
to reflect most severe problems with verbal sequencing and abstraction skills, with relative
strengths in visuospatial or rote memory skills. This finding suggests the importance of defects in
language-related functions.
Unusual or precocious cognitive or visuomotor abilities occur in some autistic children. The
abilities, which may exist even in the overall retarded functioning, are referred to as splinter
functions or islets of precocity. Perhaps the most striking examples are idiot or autistic savants,
who have prodigious rote memories or calculating abilities, usually beyond the capabilities of
their normal peers. Other precocious abilities in young autistic children include hyperlexia, an
early ability to read well (although they cannot understand what they read), memorizing and
reciting, and musical abilities (singing or playing tunes or recognizing musical pieces).
Differential Diagnosis
Autism must first be differentiated from one of the other pervasive developmental disorders such
as Asperser's disorder and pervasive developmental disorder not otherwise specified. Further, it
must be differentiated from other developmental disorders, including mental retardation
syndromes and developmental language disorders. Other disorders in the differential diagnosis
are schizophrenia with childhood onset, congenital deafness or severe hearing disorder,
psychosocial deprivation, and disintegrative (regressive) psychoses. It is sometimes difficult to
make the diagnosis of autism because of its overlapping symptoms with childhood
schizophrenia, mental retardation syndromes with behavioral symptoms, mixed receptive-
expressive language disorder, and hearing disorders. Because children with a pervasive
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developmental disorder usually have many concurrent problems, Michael Rutter and Lionel Hersov
suggested a stepwise approach to the differential diagnosis (Table 42-2).
Table 42-2 Procedure for Differential Diagnosis on a Multiaxial System
1. Determine intellectual level
2. Determine level of language development
3. Consider whether child's behavior is appropriate for
i. chronological age
ii. mental age
iii. language age
4. If not appropriate, consider differential diagnosis of psychiatric disorder according to
i. pattern of social interaction
ii. pattern of language
iii. pattern of play
iv. other behaviors
5. Identify any relevant medical conditions
6. Consider whether there are any relevant psychosocial factors
(From Rutter M, Hersov I. Child and Adolescent Psychiatry: Modern Approaches. 2nd ed.
Oxford: Blackwell; 1985:73, with permission.)