Many neuropathies, but not all, are "length dependent"--that is, the damage or "die-back" starts first at the nerve endings that are farthest from the seat of circulation and then progressively (though often slowly) continue towards more proximal regions of the body (as opposed to "distal", which describes toes, feet, fingertips). Part of the reason that the skin biopsies are taken from near the foot and the thigh is to see if this common distal/proximal gradient is going on (it is very common in toxic, metabolic, an ischemic--processes that damage blood vessels--neuropathies).
You don't seem to have this, though, which is why neuronopathy was mentioned. This is slightly different, and not length dependent, as the damage seems to occur in the dorsal root ganglia--at the level of the cell body, not the axonal (fiber) endings. There are a number of different processes that can result in a neuronopathy, many of them autoimmune, though there are many idiopathic cases as well:
These are primarily sensory, though some of the conditions that come with them have autonomic components as well, as small fibers do control autonomic functions.
By the way, here are the figures from my skin biopsy reports regarding the McArthur protocol norm determinations for nerve fiber density at calf and thigh:
Mean: +/- 1 standard deviation: Range: 5th percentile:
21.1 +/-10.4 2.9--57.5 5.2 (Thigh)
13.8 +/-5.6 0.6--32.2 3.8 (Leg)
These figures are expressed as number of distinct fibers per millimeter of skin, and are normed for males 40-49 (which I was at the time); I'll research it by I believe the figures for younger males are a bit higher, but not much.
My initial report not only showed figures below the fifth percentile, but also noted "excessive branching and swelling, consistent with a small fiber neuropathy". I did not have any autonomic symptoms--just very severe small fiber nerve pain body-wide (that came on acutely--in hours). My last biopsy--the good thing about them is they can be done repeatedly for comparison--showed me up to about 16th and 18th percentile at leg and thigh, respectively--I have gotten re-enervation and this corresponds to the reduction of symptoms. (I'm due for another one soon.) However, the problem is we have no idea how this compared to my nerve fiber density before my acute onset on April 11 2003.
Many small fiber neuropathies do have some autonomic involvement as part of the package, although sensory nerves may be affected more than autonomic ones (and vice versa); often the autonomic effect is slight or "sub-clinical" and only noticed with very exact measurements/testing:
I suspect you are experiencing some sort of small-fiber syndromes with both sensory and autonomic features, and it may not be length-dependent. But as you can see, this is not uncommon, unfortunately.