Chromosome X and Autistic Disorders

The Exploring Autism website recognizes that many researchers suspect that this particular chromosome is linked to autism and other pervasive developmental disorders aside from Rett's syndrome.

Since more males than females have autism in general, researchers automatically suspect the X chromosome because males have only one while females have two. If there is a defect on one X chromosome in females the other will compensate for it. Males do not have such compensation so the defect will manifest itself developmentally and physically.