Deb,
We have a son who has been diagnosed PDD-NOS.  He is now five years old.
He has been on a gluten and casein free diet for one year now and is showing
steady improvement.
The following is a very well written web site with a document I think you'll
want to read about gluten/casein and the possible connection to PDD or autism.
In this document Lisa Lewis refers you to researchers at the University of
Florida who have some very strong theories about this connection.  My wife and
I have worked closely with them (the research is headed up by Dr. Cade) and
have had the blood test mentioned in the article done on our son, Garrett.
His tests came back positive and we immediately put him on the gluten/casein
free diet.  After 8 months we repeated the blood test and found that his
condition had improved greatly.  Shortly thereafter came some significant
positive changes in Garrett and he continues to improve.
Please check this site out and seriously consider its content.
Regards, Keith Chambery

http://members.aol.com/lisas156/index.htm