It could have just been some other chronic virus going on. Doctors don't know what causes rheumatoid arthritis so often can't really know what's going on in the beginning?
I suspect that since nothing has "happened" in the 1-2 years with the elevated levels, that does look a little suspicious, the arthritis should be eating away at things?

http://www.mayoclinic.com/health/rhe...020/DSECTION=6