--that is, nerve dmage to the small, unmyelinated fibers that subsume the sensations of pain and temperature, as well as most autonomic functions, is that most "standard" blood tests will not show a probable cause of it (unless it is diabetic in nature), and current nerve condcution study technology cannot detect it, as these can only grossly measure the function of larger, myelinated nerves.

This is why specialized testing, such as quantitative sensory testing, sudomotor axon reflex testing, or skin biopsy might be in order. Recently, too, a new technique is coming into play--microscopic examination under flourescence of Meisner corpucles.

So, in essence, yes, many with small-fiber neuropathy will shoe as "normal" on standard examination and testing. Marc Triehaft really makes a pointof this in his article about small-fiber neuropathies:

http://www.thecni.org/reviews/13-2-p07-treihaft.htm