Down Syndrome and Pervasive Developmental Disorders

Micaela Nordhauser, M.D.
Developmental Pediatrician
Center for the Disabled
314 South Manning Boulevard
Albany, NY 12208
(518) 437-5624
Office Manager:
  Reprinted from the Down Syndrome Aim High Newsletter News and Notes with the permission of the author
© 1997 Micaela Nordhauser
All rights reserved

The pervasive developmental disorders are neurologically based behavioral syndromes, which likely result from anatomical and/or neurochemical alterations of the brain. The pervasive developmental disorders include autistic disorder and pervasive developmental disorder not otherwise specified (PDDNOS). These disorders are characterized by three primary areas of impaired function. These are qualitative impairment in reciprocal social interaction; qualitative impairment of verbal and nonverbal communication and imaginative activity; and a markedly restricted repertoire of activities and interests. These features begin in infancy or toddlerhood. Diagnostic criteria for autism and PDDNOS are delineated in the Diagnostic and Statistical Manual of the American Psychiatric Association. Children are given a diagnosis of autism if their behavioral characteristics meet a given number of criteria in each area of impairment. Children who have significant deficits in social interaction and language, but do not have a spectrum of behaviors that fulfill the specified number of criteria, are given a diagnosis of PDDNOS. The term Asperger syndrome is sometimes used to describe children who have normal cognition and mild features of pervasive developmental disorder (PDD). PDDs were at one time viewed as emotional disturbances . . . now it is understood these disorders stem from neurological impairment.

Pervasive developmental disorders were at one time viewed as emotional disturbances caused by cold, distant parents. It is now understood that these disorders result from neurological impairment. The social isolation seen in autism results from impaired processing of social information. Children may exhibit remarkably diminished awareness of the existence or feelings of others. They may have diminished direct eye contact. They may have difficulty in interpreting tone of voice, facial expression, and body language. They may have difficulty in establishing normal interpersonal relationships and peer friendships. Children with PDD may demonstrate abnormal social play, or prefer solitary play. A child with PDD may seem indifferent or adverse to affection and physical contact. Conversely, some children with PDD may be inappropriately affectionate.

Developmental language disorder is universal in PDD. The severity of impairment of receptive and expressive language varies to a great degree. Some children with autism seem to be unable to process any spoken language, and are nonverbal. These children may benefit from the use of a total communication system with sign language, and communication boards. Most children with PDD do acquire some spoken language. Acquisition is delayed, and there are qualitative abnormalities. Children may display delayed or immediate echolalia; this is the repeating of words or phrases that have been heard previously. Children may repeat what has just been said by another person, or they may repeat bits and pieces of TV commercials or rote phrases. Some children will recite over-learned phrases repetitively. Children with more mild impairment may show difficulties in using language appropriately for communication. They may speak fluently with good articulation and good grammar, but will have difficulty in initiating and sustaining conversations. They may speak on a single focus without regard to the interest of the listener. They may have difficulty in conversational turn taking. They may have impaired nonverbal communication. They may not look at their conversational partner, or respond to the partner's body language.

Many children who have PDD will exhibit abnormal prosody; this is a deficit in the ability to use rhythm and intonation in speaking. This results in stilted, monotonic, or sing-song quality to speech. Children with typical developmental patterns learn the power of communication very early. At approximately one year of age they learn to use gesture to communicate; they point for wants or shake their heads no. Young children with PDD seem unaware of the power of verbal and nonverbal communication to get their needs and wants met. They may get things for themselves, or take a parent's hand and put it on a desired object. Often, they may simply cry and cry until the parent meets their needs by trial and error.

The third significant impairment in autism is a restricted and unusual repertoire of activities and interests. Some children with PDD will exhibit motor stereotypes; these are repetitive movements and mannerisms which may include hand clapping, rocking, head banging, or twirling. Some children will show unreasonable resistance to changes in their routines or environment. For these children, finding a familiar object in an unusual place, or following a different path to the store, may be very distressing. Many children with PDD seem to have an unusual tolerance for monotony. They may engage in the same play activity for hours. Some children will spend long periods shaking a string, turning a light switch on and off, or playing with water. The older more verbal child may study letters, numbers, or the phone book for hours. These children may spend months studying one topic, such as time tables, and become preoccupied with this narrow area of interest. Children with PDD may display an unusual attachment to particular objects, or preoccupation with parts of objects. They may become fascinated with wheels on toy vehicles, or other small parts of toys. Children with PDD may show a preference for manipulating, lining up, or classifying toys, rather than engaging in creative or imaginative play. In early childhood, there is an absence of symbolic or fantasy play; there is diminished play acting of adult roles.

The prevalence of autism in the general population is approximately five per ten thousand. There are few studies that address the prevalence of autism in persons with Down syndrome. Those studies available report prevalence rates of autism in Down syndrome that vary from .8% to 11.4%. The large discrepancy in prevalence rates reported may be secondary to population selection and diagnostic criteria utilized. A study by Myers and Pueschel (1991) surveyed 497 children and adults with Down syndrome who were followed as out-patients in a child development center of the Rhode Island Hospital. This study reported an autism prevalence rate of 1.2% in both children and adults with Down syndrome. This frequency of autism is comparable to that of persons with mental retardation of unspecified etiology. It is significantly greater than that seen in the general population. The reason for the development of infantile autism in persons with Down syndrome is not clear. The behavioral features of autism may result from differences in brain structure or function which are a direct effect of the presence of Trisomy 21. It is also possible, however, that the increased rate of autism may be seen secondary to increased vulnerability of infants with Down syndrome to diminished oxygen levels, infections, and other noxious events, either prenatally or in infancy. If we feel there has been a change in our child's emotional or behavioral profile, we may need to be persistent with professionals working with our child to obtain a full evaluation.

Children with Down syndrome are at risk for underdiagnosis of concurrent developmental disorders. Some clinicians tend to stereotype the personality of children with Down syndrome. They are predisposed to see children with Down syndrome as unusually happy, affectionate, and good-natured. The majority of studies support that children with Down syndrome are as diverse in temperament as are typically developing children. The predisposition on the part of some physicians to see all children with Down syndrome as sociable may interfere with the physician's perception of deficits in social relatedness. In addition, the majority of children with Down syndrome do have delays in communication skills. In a child with Down syndrome and autism, these delays will be of a more profound nature. Some physicians may inappropriately attribute profound communication impairments to the diagnosis of Down syndrome, without considering that a secondary developmental disorder may be present. It is important for children and their parents that each child's developmental difficulties are clearly understood, with appropriate diagnosis being given. Until the correct diagnosis is made, parents are not provided with appropriate information which will allow them to best understand their child's difficulties. Professionals working with a child will not be made aware of possible pharmacological interventions for children with autism. At this time there is a great deal of research looking at the possible use of medicine in the treatment of the pervasive developmental disorders.

While this discussion has focused on the concurrence of autism in children with Down syndrome, it should be mentioned that persons with Down syndrome are at significant risk for other neuropsychiatric disorders as compared to the general population. Again, professionals working with children may be likely to attribute features of a neuropsychiatric disorder to the child having Down syndrome, and not appropriately investigate the child's symptoms. If as parents we feel there has been a change in our child's emotional or behavioral profile, we may need to be persistent with professionals working with our child to obtain a full evaluation. Although it may be difficult to pursue a secondary diagnosis for our children, we should be assured that it will be to our child's benefit to identify and treat any concurrent developmental or neuropsychiatric difficulties.