8. What are the causes of autism?

The causes for autism are most likely genetic. In most kids who present with a mild form of autism, such as in PDD NOS, despite a very extensive workup that may include blood test, urine tests, imaging studies, and other tests, everything comes back normal. The general consensus is that autism and PDD NOS are genetic disorders that can't be identified in current genetic testing. This may never become specifically identified in the future because "autism" is a general term of a behavioral pattern that may be caused by several different genetic abnormalities. This means that different genes or different combinations of defective genes may result in the same presentation of PDD NOS or autism.

Identified causes for autism include several chromosomal abnormalities involving different "genetic sites." Fragile-x syndrome involves the x chromosome, Angelman's syndrome involves chromosome 15, and many other chromosomal abnormalities may present with "autism." Other disorders such as Touberouse sclerosis, a disorder causing skin and brain abnormalities and frequent severe epileptic seizures (chromosome 9 and 16) may present with "autism" also. Some "metabolic disorders" such as PKU (phenylketonuria), where a substance (phenylalanine) accumulates in the brain, and other disorders of metabolism may present with autism.

Another important condition that may cause "autism" is a form of a seizure disorder or Laundau Kleffner syndrome. This disorder, also known as acquired epileptiform aphasia, is a disorder in which seizures develop from the area responsible for speech (in the left hemisphere), "robbing" the child from acquiring language and is associated with an autistic regression.