Here's a link to an interesting talk and write-up on the subject of fibromyalgia and SFN and how a significant number of people diagnosed with the former show SFN when a punch biopsy was done. He's careful not to say that fibro was a mis-diagnosis, but rather that SFN could be an add-on problem.

Dr Charles Argoff, professor of neurology at Albany Medical College and director of the Comprehensive Pain Center at Albany Medical Center

http://www.medscape.com/viewarticle/838857