--there are a number of known hereditary/genetic varieties of neuropathy that affect predominantly small-fibers and that can be tested for.

A doctor that won't order such testing is either uniformed or lazy, as results from somen of these may affect a treatment plan. If the former, you can educate him/her, if the latter, let him/her refer you to a center that will do such testing (or perhaps you can get there yourself--you probably already know about Mayo, Hopkins, Cornell-Weill, Jack Miller, Columbia-Presbyterian, Masssachusetts General, Jacksonville Shands, etc.--just from reading here . . .)

And take a look at:

http://www.neuro.wustl.edu/neuromusc...ory-small.html

http://www.neuro.wustl.edu/neuromuscular/time/hsn.htm

You can take these to the doctors if need be.