--will not show up on nerve conduction and EMG testing, as those tests can only document damage to larger, myelinated nerves.

it is certainly possible to have neuropathy with normal nerve conduction and EMG studies--I've never had abnormal nerve conduction studies (and I've had quite a few), but my small-fiber problems have been well-documented by skin biopsy, which is still the gold standard for discovering small-fiber syndromes (although it generally won't reveal a cause).

Small-fiber problems can also be picked up through abnormal results on qualitative sensory testing or autonomic testing (tilt table, sweat testing, and the like).