Pervasive Developmental Disor... Health Article

Definition

The pervasive developmental disorders, or PDDs, are a group of childhood disorders that manifest during the first years of the child's life. They are marked by severe weaknesses in several areas of development: social interaction, communication, or the appearance of stereotyped behavior patterns and interests. The PDDs are also known as autistic spectrum disorders. As the phrase spectrum disorder suggests, persons with these disorders fall at different points along a fairly wide continuum of disabilities and associated disorders. As defined by DSM-IV, the pervasive developmental disorders include:

• autistic disorder
• Rett syndrome
• childhood disintegrative disorder (CDD)
• Asperger syndrome
• pervasive developmental disorder not otherwise specified (PDD-NOS)

Description

The PDDs form a diagnostic category intended to identify children with delays in or deviant forms of social, linguistic, cognitive, and motor (muscular movement) development. The category covers children with a wide variety of developmental delays of differing severity in these four broad areas. The precise cause(s) of the PDDs are still obscure, but are assumed to be abnormalities of the central nervous system.

Autistic disorder

Autistic disorder, or autism, was first described in 1943. Autistic children are characterized by severe impairment in their interactions with others and delayed or abnormal patterns of communication; about 50% of autistic children do not speak at all. These abnormalities begin in the first weeks of life; it is not unusual for the parents of an autistic child to say that they "knew something was wrong" quite early in the child's development. Another characteristic symptom has been termed "insistence on sameness;" that is, these children may become extremely upset by trivial changes in their environment or daily routine—such as a new picture on the wall or taking a different route to the grocery store. Autistic children often make repetitive or stereotyped gestures or movements with their hands or bodies. Their behavioral symptoms may also include impulsivity, aggressiveness, temper tantrums, and self-biting or other forms of self-injury.

About 75% of children diagnosed with autism are also diagnosed with moderate mental retardation (IQ between 35 and 50). Their cognitive skills frequently develop unevenly, regardless of their general intelligence level. A minority of autistic children have IQs above 70; their condition is sometimes called high-functioning autism, or HFA. In addition to mental retardation, autism is frequently associated with other neurological or medical conditions, including encephalitis, phenylketonuria, tuberous sclerosis, fragile X syndrome, and underdeveloped reflexes. About 25% of autistic children develop seizure disorders, most often in adolescence.

Rett syndrome

Unlike autism, Rett syndrome has a very distinctive onset and course. The child develops normally during the first five months of life; after the fifth month, head growth slows down and the child loses whatever purposeful hand movements she had developed during the first five months. After 30 months, the child frequently develops repetitive hand-washing or hand-wringing gestures; over 50% of children with the disorder will develop seizure disorders. Rett syndrome is also associated with severe or profound mental retardation. As of 2001, this disorder has been diagnosed only in females.

Childhood disintegrative disorder (Heller's syndrome)

Childhood disintegrative disorder, or CDD, was first described by an educator named Theodore Heller in 1908. He referred to it as dementia infantilis. Children with CDD have apparently normal development during the first two years of life. Between two and ten years of age, the child loses two or more previously acquired skills, including language skills, social skills, toileting, self-help skills, or motor skills. The child may also lose interest in his or her surroundings, and often comes to "look autistic." The data available as of 2001 indicate that CDD has several different patterns of onset and development; it may develop rapidly (within weeks) or more slowly (over a period of months).

CDD is frequently associated with severe mental retardation. In addition, children with CDD have a higher risk of seizures. CDD is occasionally associated with general medical conditions (metachromatic leukodystrophy or Schilder's disease) that could account for the developmental losses, but in most cases there is no known medical cause of the child's symptoms.