I would think one of the differences between them might be the extreme fatigue factor.
Does CMP have fatigue as a sx also?
I read up on these back in 04/05 when I was trying to help drs figure out what I had.. but haven't researched on it lately.
I do like Devin J. Starlanyl's site - seems to explain a lot of it logically & clearly.
http://homepages.sover.net/~devstar/define.htm