Below is an article that appeared yesterday in the LA Times.  It looks at the differences in spectrum severity depending on the age that the autism symptoms develop.  Apparently, children with regressive autism, who start out developing typically and then regress are more likely to have long term severe autism.  Here is a link to the piece in the LA Times as well as the original source material. (The Journal of Autism & Developmental Disorders)

http://latimesblogs.latimes.com/booster_shots/2010/04/autism-symptoms-regression.html

http://www.springerlink.com/content/w466422333j42521/?p=dab1468d1fde464aae0917e6c4dfdb90&pi=5