Office for People With Developmental Disabilities

Print: Print this page

Pervasive Developmental Disorders


Autistic Disorder: Sometimes called “classical autism,” Autistic Disorder is the most common ASD. Onset occurs before the age of three and is characterized by significantly delayed or unusual verbal or nonverbal communication skills and social interactions, as well as unusual, repetitive behaviors, and/or severely limited activities and interests. Individuals with Autistic Disorder have difficulty making eye contact, reading other people’s faces, nonverbal cues and gestures, and interacting with others. They may engage in repetitive or unusual movements such as twirling, rocking, hand flapping or clapping, posturing, or self-abusive behavior such as head-banging, slapping or biting themselves. They tend to speak later in life, if at all, and may refer to themselves by name instead of using “I” or “me. Echolalia – the repeating of all or part of what is said to them by someone else – is another common speech pattern among individuals with Autistic Disorder.

Asperger Syndrome: Individuals with Asperger Syndrome generally do not have language or cognitive delays but do have impairments in social behavior and communication and display unusual behaviors and interests. They may have unique speech patterns, or speak in a monotone or rhythmic voice. They often have difficulty engaging in conversations, reading social cues, and developing social relationships. They may also find it difficult to express and classify their feelings or to connect with and understand others’ experiences. It is not uncommon for individuals with Asperger Syndrome to develop an obsessive interest in one narrow, specific subject and to become ‘experts’ on that subject. They can also be sensitive to different stimuli, such as sounds or noise level, the texture of certain materials, or certain foods or types of food, and they often follow strict schedules to feel in control.

Pervasive Developmental Disorder — Not Otherwise Specified (PDD-NOS): If a child has symptoms of autism, but does not meet the specific criteria for a diagnosis of Autistic Disorder or Asperger Syndrome, a diagnosis of PDD-NOS is given. As with Autistic Disorder, this condition is recognized by marked difficulties in communication, social interaction with peers, and/or stereotyped behavior patterns or interests. Children with PDD-NOS display a range of traits. They may lack interest in interacting with other children and seek to avoid them altogether. They may enjoy some interaction, but still be unsure of how to behave with others, or they may tend to become over stimulated easily. Some may experience unusual sensitivities to certain events or objects in their environment or have a strong need for sameness and routine and react poorly to change. Some children may engage in noticeable movement patterns such as hand-flapping or twisting, toe-walking, lunging, darting, pacing, jumping, body rocking, and head rolling or head-banging.

Rett Syndrome: Rett Syndrome, also known as Rett’s Disorder, is a rare genetic disorder that almost always affects females. It occurs at a rate of about one in every 10,000-15,000 female births. It is included among the Pervasive Developmental Disorders because in its early stages it resembles autism. Like the other disorders, this condition ranges from mild to severe in its expression. Development is normal during the first six to 18 months of life. At some point during this time, however, parents may notice a change in their child’s behavior and the loss of muscle tone and related abilities such as walking and hand use. Changes in the rate of head and brain growth, development of speech and reasoning, and the repetition of meaningless gestures, such as hand-wringing or hand-washing gestures, also occur. Approximately eight in 10 girls with Rett’s Disorder are prone to seizures.

Childhood Disintegrative Disorder (CDD): Also called Heller’s Syndrome, CDD affects boys more often than girls, and is diagnosed if the symptoms are preceded by at least two years of normal development before the age of 10. CDD is an extremely rare disorder that resembles Autistic Disorder wherein a period of normal development is followed by a period in which the child loses already-developed skills. Skills loss occurs in language, self-care, toilet training, motor coordination, interest in the social environment, and social interactions. Over a period of two to four years, these children develop behaviors that appear autistic. Children who have CDD are also at greater risk for seizures.