[MysticCat]

I don't have time (or energy) this late to go into it too much, but my son has Asperger's, a form of high-fuctioning autism. Most people probably wouldn't notice too much amiss except some social awkwardness unless they spent a fair amount of time with him. (Parents of kids on the autism spectrum usually pick up on it pretty quickly, though.)

Autism Spectrum Disorders (not diseases) literally are that -- disorders found on a spctrum from high-functioning to low-functioning. While there are commonalities, there are also a wide variety of differences. Every person on the spectrum will be different.

As for cause, I think most parents I know subscribe to something of a "perfect storm" theory -- that just the right (or wrong) mix of environmental and genetic factors combine to prevent proper neuroligical development.