The pervasive development disorders are a group of conditions, containing: autism, Asperger's syndrome, Rett's syndrome, childhood disintegrative disorder and pervasive development disorder not otherwise specified.

Children with autism have problems in communicating and relating to other people, they have problems with the imagination and with the understanding of reality. In many cases, there can appear some degree of mental retardation.
The children with Asperger's syndrome have average or above average intelligence, they develop normally in the areas of language and cognition, but they have problems with social interaction and communication, a narrow range of interests and often have difficulty concentrating and poor coordination.
The children with Rett's syndrome have the symptoms mentioned before, but the also suffer the loss of many motor or movement skills. This condition affects usually girls, because it is linked to a defect on the X chromosome.
Childhood disintegrative disorder is a rare condition and children affected by it begin their development normally, but between the age of 2-10 many of the developed skills will be lost. Those affected by this illness may lose control of other functions, including bowel and bladder control.
Pervasive development disorder not otherwise specified refers to children that are too social to be considered autistic, but they still have some difficulty interacting with others, communicating and playing.

Children with pervasive development disorders can develop a lot of symptoms and the severity of them depends from case to case. Some general symptoms include difficulty with social interaction, understanding the reality, with verbal communication, problems using and understanding language, repetitive body movements or patterns of behavior. There can also be mentioned difficulty sleeping, aggressive behavior, and nervousness.
The cause of these illnesses is not known yet, but researchers are working on it. However, there were studies that suggested that these illnesses are caused by a problem with the nervous system, and there are studies in progress that are examining the structure and function of the brain in people with autism, to find out clues that will lead to a better understanding of these illnesses.

It is known that in 10.000 births, there appear 5-15 cases of children affected by these pervasive development disorders. The most affected are the boys, excepting the situation of Rett's syndrome, which affects mostly girls.
In order to diagnose autism, if the symptoms are present, the doctor will perform a complete medical history and physical examination. Then, he will do some tests, like X-rays and blood tests, to see if there are symptoms that can show a physical disorder. If there isn't found a physical disorder, the child is sent to a specialist in childhood development disorders which is trained to diagnose and treat the pervasive development disorders. The doctor analyzes the child's level of development, speech and behavior, and often can ask the parents of the child, or other adults that are familiar with him about the symptoms that they found.
Because children affected by these disorders can have a large range of symptoms, the treatment must be adjusted to fulfill every child's needs.
Treatment can include medications in order to treat specific symptoms, like anxiety, hyperactivity and behavior that may result in injury, there are also necessary therapies that increase the child's functional abilities, and strategies for supporting positive behavior.
The result seen in people with pervasive development disorders varies depending on the type and severity of the condition, on the age when the treatment started and on the availability of supportive resources for the child.

There are being made researches in order to find out more about these conditions, to discover what is happening in the brain and to find better ways for diagnosing and treating these disorders, or even prevention and cure.

For more information about autism causes please review http://www.autism-info-center.com/signs-of-autism.htm or even http://www.autism-info-center.com/autism-symptoms.htm