--just because one's intraepidermal nerve fiber density falls between the 5th and 95th percentile, and is therefore read acccording to the protocols as "normal", doesn't mean one doesn't have a neuropathic process going on, It depends on when the skin biopsy is done--at what stage the process may have been "caught"--and, of course, at what level of density one started (though this is hard to know, since there's no reason to do this kind of biopsy to enumerate nerve density and examine condition if one is asymptomatic, unless, like McArthur's original subjects, there's an attempt to establish a control group).

Pain levels do not correlate well at all to density levels; there may be a bit more correlation to observed condition of the fibers, especially if swelling an excessive branching of individual fibers is observed (and yes, the latter is an attempt to re-establish function in areas in which nerves are under attack, so it can be a hint there is an attack ongoing when found). Remember, regrowing nerves can be as painful as dying ones, at least for a while, until the brain learns how to interpret these new signals.

My sense has been that often pain is actually worse during an ongoing process; if one's nerves are completely killed off, one tends to get more numbness than pain, as there's less there to record sensations anymore. Of course, many have reported both in an area simultaneously--certain patches have died, certain patches are dying, certain others may be frantically trying to re-grow. In fact, many neuros take the sharp, burning pain as a sign of damaged nerves, not (yet) dead ones, and actually look upon this with a more favorable prognosis than they do numbness, though I doubt the patients find this "better".