Pervasive Developmental Disorders: The Autism Spectrum Disorders

Pervasive developmental disorders (PDDs) are also referred to as the autism spectrum disorders (ASDs). There are five disorders in this category: autism, Asperger disorder, Rett disorder, childhood disintegrative disorder, and pervasive developmental disorder, not otherwise specified (PDD, NOS). The core feature of the PDDs is an abnormal relatedness and social development. Although cognitive and motor development are often also affected, it is the manner of relating and communicating that is the sine qua non of the disorders.

These are tragic yet fascinating disorders. Although the movie Rainman was fiction, individuals with ASDs may be high functioning in many ways, but experience an extreme need for sameness and routine, lack of flexibility, inability to read social cues and interact in a reciprocal manner, and odd speech. The term “spectrum” is sometimes used to denote the fact that the level of impairment and disability can be quite variable.

At one time, individuals with ASDs were thought to be resistant to intervention. We now know that early multimodal and multidimensional treatment may markedly improve prognosis. Support for the family, in addition to the child, is also required. Psychiatrists work within a system of care to provide needed services for a child and his or her family.

Basic Principles

From the earliest description of autism by Leo Kanner in 1943, the disorder has been studied widely to ascertain the etiology and effective treatments. Some initial descriptions of “refrigerator mothers” as the cause has been long since dispelled. A neurological insult of multiple etiologies (genetic, intrauterine, neurotransmitter, or neurophysiological abnormalities) is posited. Parenting patterns do not cause autism. However, high parental skill level in working with his/her child may improve prognosis.

Although many children with more severe forms of ASD may be identified early, I find that schools commonly request consultation for children with mild “spectrum” disorders in the early elementary years. These children often present with tantrums as a key concern. The demands of school (for socially appropriate and conforming behavior) and the exquisite sensitivity of an ASD child to overstimulation, poor social and coping skills, and extreme need for sameness may overwhelm these youngsters. Oppositionality, obsessive-compulsive behaviors, and

behavioral outbursts may be the primary complaint. A full evaluation followed by recommendations that allow the child to feel comfortable and not overwhelmed in the educational setting is often crucial to the child’s ability to learn and the school’s ability to provide for him or her.

Diagnostic Criterion and Epidemiology

It is estimated that 1% of the population may have a diagnosable autistic spectrum disorder. The number of children diagnosed with ASD has increased rapidly in the last 10 years, probably due to increased rate of detection of milder forms of the disorder, as well as potentially genetic or environmental contributors. The prevalence is greater in boys (except for Rett disorder). Girls with the disorder tend to be more severely affected. ASDs present in equal prevalence across race, ethnicity, and nationality. Table 5.1 summarizes the diagnostic criteria and epidemiology of the PDDs. Tables 5.2 and 5.3 summarize the etiology and differential diagnosis.

Comorbid Mental Disorders

Comorbidity is common with the ASDs. It is estimated that up to 80% of children with autism also have mental retardation. Anxiety disorders, obsessive-compulsive disorder, and attention deficit hyperactivity disorder are all quite common. Tic disorders and psychotic symptoms are also notable comorbidities. Of note, a number of chromosomal disorders (especially fragile X and tuberous sclerosis) present with autistic-like features. Intrauterine viral infections, phenylkenouria, and seizure disorders are also associated. Table 5.4 summarizes components of a thorough evaluation.

Table 5.1 Characteristics of the Pervasive Developmental Disorders

Disorder	Prevalence	Clinical Findings	Clinical Course
Autism	2–15 per 10,000 Boys, 4; Girls, 1 Girls generally with more severe disorder	Severe impairment of social interaction and communication Restricted, repetitive, and stereotypic patterns of behavior, interest, and activities Onset before age 3 Mental retardation common	Lifelong course Language skills and overall IQ are strongest prognostic indicators 25% have seizures in adolescence
Asperger disorder	Estimated 10–36 per 10,000 Boys, 5; Girls, 1	Impairment in social interactions Preoccupation with one or more restricted patterns of interest No delay in language or cognitive development Nonverbal learning disability cognitive profile common Motor clumsiness	Lifelong course Seem to improve as they mature Superior IQ improves prognosis 1/3 develop comorbid psychiatric disorders
Childhood disintegrative disorder	Estimated at 0.11 per 10,000 Boys, 8; Girls, 1	Normal development for at least 2 years Severe loss of developmental skills before 10 years of age	Skill loss usually occurs over a 6–9 month period, then plateaus Poor prognosis Mental retardation
Rett disorder	0.44 to 2.1 per 10,000 Girls only (rare reports of boys)	Normal at birth, but onset by 2 years Deceleration of head growth Loss of motor skills with hand-wringing movements; gait disturbance Loss of language Loss of social engagement	Severe regression in skills by age 2 Physically and socially debilitating High mortality (1.2%/yr)
PDD, NOS	2–16 per 10,000 Boys > Girls	“Atypical autism” Does not meet criteria for autism because of late age of onset, atypical symptoms, or subthreshold symptoms	Lifelong, but variable outcome Frequent comorbid psychiatric disorders