Our son was diagnosed and has received intense IBT/ABA therapy (along with spech, OT and PT). It has been fantastic. Total turn around.
No low gluten diet, Jenny McCarthy BS, just Cognitive Behavioral Therapy http://en.wikipedia.org/wiki/Cognitive_behavioral_therapy .
Sadly as of the latest information I have, we don't know what causes Autism and CBT is one of the only effective means for treating it.