I've encountered an individual who had fibro, me/cfs, pots diagnosis. Turns out his small nerve fibers were fried by an antibiotic. His skin punch biopsy showed reduced fibers. This may not be the case in everyone, but SFN is extremely under diagnosed.

He was a chemist, and he ended up healing all his symptoms with pirenzepine. If I recall correctly they did the skin punch biopsy again and his physician was stunned when they saw regrowth of the fibers.

Today, WinSanTor is in stage 3 trials with their drug. They designed a cream with main ingredient being pirenzepine. They are targeting diabetes but the med appears to work for small nerve fibers as well.

Small nerve fibers control so much that any time people have weird unexplained symptoms it should be explored.