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.)