The term "pervasive developmental disorders," also called PDDs, refers to a group of conditions that involve delays in the development of many basic skills. Most notable among them are the ability to socialize with others, to communicate, and to use imagination. Children with these conditions often are confused in their thinking and generally have problems understanding the world around them.
Because these conditions typically are identified in children around age 3 -- a critical period in a child's development -- they are called developmental disorders. The condition actually starts far earlier than age 3, but parents often do not notice a problem until the child is a toddler, when differences in children of the same age can be more obvious or noted. These children may still not be walking, talking, or developing in the same way as their peers.
Autism Spectrum Disorders
The forms of autism are thought to overlap considerably. But the fact that
there is wide variation in symptoms among children with autism led to the
concept of autism spectrum disorder.
Autism seems to be on the rise, and autism spectrum disorders affect between
two and six children out of every 1,000 in the U.S. It's unclear, though,
whether the growing incidence of autism represents a real increase or just
Early diagnosis of an autism spectrum disorder is important. That's because
detection leads to treatment, and with early treatment, a child with autism can
gain improved language and social skills.
Autism: Children with autism have problems with social interaction, pretend play, and communication. They also have a limited range of activities and interests. Many -- nearly three out of every four -- children with autism also have some degree of intellectual disability. Children with autism can frequently have seizures as well as low muscle tone. They also have underlying anxiety and resistance to change.
Asperger's syndrome: Like children with autism, children with Asperger's syndrome have difficulty with social interaction and communication. They also have a narrow range of interests. However, children with Asperger's have average or above average intelligence and develop normally in the areas of language and cognition (the mental processes related to thinking and learning). Children with Asperger's often have difficulty concentrating and may have poor coordination. Asperger's is usually not recognized until children have enough language skills to show a limited focus and unusual patterns of speech.
Childhood disintegrative disorder: Children with this rare condition begin their development normally in all areas, physical and mental. At some point, usually between ages 2 and 10, a child with this illness loses many of the skills he or she has developed. In addition to the loss of social and language skills, a child with disintegrative disorder may lose control of other functions, including bowel and bladder control.
Rett syndrome: Children with this very rare disorder have the symptoms associated with a PDD and also suffer problems with physical development. They generally suffer the loss of many motor or movement skills -- such as walking and use of their hands -- and develop poor coordination. This condition has been linked to a defect on the X chromosome, so it almost always affects girls.
Pervasive development disorder, not otherwise specified (PDD-NOS): This category is used to refer to children who have significant problems with communication and play, and some difficulty interacting with others, but are too social to be considered autistic. It's sometimes referred to as a milder form of autism.