Autism - Causes

Autism is a brain disorder that affects the way the brain uses or transmits information. This disorder almost certainly develops before the child is born. The problem may be located in parts of the brain that process information that comes from the senses, such as the eyes and ears.

Autism appears to be a genetic disorder. Identical twins are more likely to both have the disease than are fraternal twins. Identical twins have exactly the same genetic make-up. Fraternal twins do not. In a family with one autistic child, the chance of having a second autistic child is about one in twenty. That rate is fifty times greater than in the general population.

Relatives of autistic children sometimes display autistic-like behaviors. For example, they may have problems communicating with other people, or they may repeat certain behaviors over and over again. They may also have certain emotional disorders.

In a few cases, autistic behavior is caused by a disease, such as rubella (German measles; see rubella entry) in a pregnant woman, encephalitis (pronounced in-seh-fuh-LIE-tess; brain fever; see encephalitis entry), or phenylketonuria (pronounced fen-uhl-keet-n-YOOR-ee-uh, PKU) left untreated.