Subject: Many symptoms of autism and Tourette are similar. Why?

My children and I have Tourette Syndrome.  My son has an ADHD 
and some large and small motor impairment, although he is very 
bright otherwise.  Anyhow, while my son was taking occupational 
therapy to improve his balance and handwriting, the other moms 
and I would discuss our kids; many of the mothers of autistic 
children described similar behaviors--tics and obsessive 
behaviors.  Many of the autistic kids also were bright; some 
were able to communicate using language quite well.  Is this an 
accidental congruence of symptoms or is there some underlying 
genetic link between these conditions? 

Re: Many symptoms of autism and Tourette are similar. Why?