Pervasive Developmental Disorder
Joseph Piven, MD, Associate Professor of Child Psychiatry.
Christian Plebst, MD, Fellow, Child Psychiatry.
Department of Psychiatry, University of Iowa Hospitals and Clinics.
Spring 1997.

Differentiating between autism and pervasive developmental disorder (PDD) can be difficult. Pervasive Developmental Disorder, Not Otherwise Specified (PDD,NOS) is a disorder that has milder symptoms than autism. Diagnosis can be difficult because the boundaries between the two remain somewhat arbitrary. PDD,NOS has only recently been recognized by DSM-IV, and further research is needed to determine whether autism and PDD are part of a single pathology with the same etiology, or do in fact represent two distinct syndromes.

The prevalence rate of autism is about 2 to 5:10,000. It is 4 to 5 times more frequent in males. Females with autism are more likely to also have a diagnosis of severe mental retardation. Prevalence data for PDD are more limited, but suggest that this disorder occurs in about 20:10,000 school-age children.

The underlying etiology of autism is believed to be biological, as evidenced by the:

• High rate of association of autism with mental retardation (70%).
• 4-5:1 male:female ratio.
• Association of autism with an increased incidence of seizure disorders (20%).
• High concordance rate for autism in monozygotic (65%) versus dizygotic twins (approximately 3-5%).
• Increased recurrence risk of autism in siblings (100 times the population rate, or about 5%).
• Post mortem and imaging studies frequently show abnormal brain structure in persons with autism.

Kevin

Kevin, a 7-year-old diagnosed with PDD, NOS, is the third of three children born to college-educated parents. His mother's pregnancy was unremarkable. Kevin's parents had always felt that he was different in some way from his siblings; he played more roughly, and his social skills were poor, though he wanted to participate in games and be with others, a characteristic different from the aloofness seen in children with autism.

Kevin lacked normal prosody (inflection) in his speech, and was overly formal in his choice of words. His conversation skills were poor and he had a difficult time correctly interpreting even the most obvious jokes. However, he never exhibited the more characteristic language abnormalities of autism, such as language delay, immediate and delayed echolalia, and pronoun reversal.

Once in school, Kevin was quickly identified by his classmates as "odd," which led to frequent teasing. He often misjudged the social context, and made odd comments that put off the other children. His academic performance was acceptable, although he continued to struggle with expressive and written language. In the past, school staff often called his parents to talk with them about his "oppositional" behaviors, which they felt reflected a "parenting problem."

Kevin's parents describe him as strong willed and stubborn, always wanting things done his way. For example, his food must be carefully arranged on his plate so that different foods do not touch. If they do, he refuses to eat, or throws down his food and stamps off. He likewise becomes distressed with changes in his environment, such as having a substitute teacher.

Kevin's case may sound very familiar. Although he exhibited no gross abnormalities in speech or motor development, he was more active and unpredictable than his siblings, traits that prompted visits to a variety of professionals and led to early diagnoses of attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD). It is not uncommon for children with PDD to receive a number of different diagnoses that describe components of their behaviors -- ADHD, ODD, conduct disorders, and expressive and receptive language disorders. Children with PDD can indeed be hyperactive, inattentive, oppositional, violent, and aggressive -- but these diagnoses are considered aspects of PDD.

Evaluating Kevin

In trying to determine a diagnosis, we focused on Kevin's history when he was between 4 and 5 years old, an age when PDD behaviors are often most obvious. We felt that Kevin's behaviors were characteristic of PDD, NOS. He had impaired social skills; a history of mild language deficits; and behavioral rigidity. The diagnosis of autism is generally reserved for children with more severe deficits than those we observed in Kevin.

Accurate diagnosis

Early diagnosis and treatment of PDD is important. Recent studies suggest that early intervention in autism, with educational programming and intensive behavioral training, may have a substantial effect on outcome. Although studies have not yet been undertaken, it seems likely that similar findings about PDD will eventually be reported. Children who are suspected of having PDD should be referred to an experienced tertiary center for multidisciplinary evaluation. This usually includes psychiatric, psychological, educational, language, and physical assessment. The child's individual needs and strengths, as determined during the assessment, will provide the foundation for a treatment plan.

Clues to appropriate social development In the office, observing the following behaviors can give you some insight into whether a 4- to 5-year-old is developing normal social skills: Spontaneous and appropriate affection toward parents or family. Spontaneous, appropriate greetings to parents. Seeking comfort from appropriate adults when the child is frightened or hurt.

Approaches that have been used with good results with children who have PDD include:

• Behavioral approaches aimed at improving social skills and expanding the individual's behavioral repertoire (for example, to decrease rigidity).
• Speech therapy.
• Medications such as selective serotonin re-uptake inhibitors (SSRIs).

Resources

_____. Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV); and Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Primary Care Version (DSM-IV-PC) (Washington: American Psychiatric Association, 1994 and 1996).

Cook Jr. E and Leventhal B (1995). Autistic disorders and other pervasive developmental disorders, in Riddle, M, Child and Adolescent Psychiatric Clinics of North America, 4(2):381-399).

Lord, C and Rutter M (1994). Autism and pervasive developmental disorders, in Rutter, M et al. Child and Adolescent Psychiatry, 3rd ed. (London: Blackwell Scientific Publications, 569).

Powers, M (1989). Children with Autism, A Parents' Guide (Silver Spring, MD: Woodbine House).

Siegel, B (1996). The World of the Autistic Child (Oxford: Oxford University Press).