--the original paper by Dr. Abhey Mogehkar of John's Hopkins on small-fiber neuropathy secondary to damage at the level of the dorsal root ganglia (which I haven't been able to find an active link to this morning, though I think I actually have a hard copy somewhere in my files) does mention that one of the distinguishing characteristics leading to suspicion of DRG involvement is when the skin biopsy results are NOT length-dependent.
Also, see this description from the Washington University neiromuscular website:
http://neuromuscular.wustl.edu/antib...uron.html#sfsn