Autism is a type of developmental disorder in which the affected person lacks in social communication in both verbal and nonverbal means and also shows the characteristic repetitive behavior. As per the diagnostic criteria the above mentioned symptoms must become evident within first three years of life.
In autism there is alteration in the ways the nerve cells connect and communicate with one another, resulting in the abnormal processing of information from the brain however, how or what precipitates these changes is not known. Genetic factors are known to play an important role in causing autism.
The disease is not very rare; worldwide per 1 to 2 out of 1000 people suffer from autism and boys are more commonly affected. Although autism is not totally curable; still interventions like cognitive, behavior and speech therapy when started early help the affected child to lead a normal social life to a certain extent.
Currently, some people do not consider autism as a disease and they believe that rather than seeking treatment for it one should accept it as a difference.
Symptoms
Usually the symptoms of autism become evident by 2 years. The symptoms worsen gradually as there is normal behavioral and cognitive development in the affected child during the first year of life.
There are some characteristic symptoms of autism like the affected child is unable to take part in pretend play, he usually lacks social skill expected from a normal child of the same age group and also suffer from poor verbal and nonverbal communication skills.
There is a certain type of autism known as regressive type in which the affected child not only fails to gain newer communication skills usual for other children of the same age group but also looses all the social skills he had gained before.
Most common presenting symptoms are
1. Excessive sensitivity towards touch, taste or smell and they become significantly distressed to do things they refuse to do
2. They become obsessed with routine and any deviation no matter how little will lead to severe degree of distress
3.Repeated stereotype abnormal body movements
4. Attachment to objects to severe degree
Other than the above mentioned symptoms certain social skill, behavior and communication related symptoms also appear.

Social skill related symptoms: these include
1. Less or no inclination to make friends
2. Less or no interest to play interactive games
3. Keeps to oneself
4. Avoidance and no response to eye contact
5. Lack of empathy often considered as cruel indifference

Behavior related symptoms include
1. Throwing of tantrum almost all the time
2. Shows abnormal level of perseveration
3. Poor attention span
4. Either over active or passive
5. Preference to solitary play
6. Normal sound may become intolerable to the child
7. Have increased or poor response to pain
8. Avoids physical contact

Communication related symptoms include
1. Inability to start or continue conversation
2. Tries to communicate with gestures and less with words
3. Poor language development
4. Inability to refer to oneself as “I”
5. Often repeats words
Causes
Although the exact underlying cause of autism is still not clear, it is established that abnormality in brain structure and chemistry are the main culprits. Genetic factors are known to play an important role, as the condition is more common in identical twins and different types of other genetic problems are known to affect families with history of autism.
Common possible risk factors, although yet to be scientifically established include diet, mercury poisoning, exposure to teratogens while in uterus etc.
Contrary to the popular belief as per the American Academy of Pediatrics no vaccine or component of the vaccines are anyway related to the causation of autism.
Treatment
Although not fully curable, treatments are available to help the affected children to adjust in the society to some extent. Common options include applied behavior analysis, certain drugs, speech therapy, physical therapy and occupational therapy.