--while skin biopsy is excellent at documenting the density and condition of the small fiber sensory nerves, it is unlikely to reveal a cause of any damage or reduced intraepidermal nerve fiber density that may be found and documented.

There are some clues that might be revealed--swelling and or "exploded from the inside" fibers might hint at an inflammatory or autoimmune process. But the samples are generally too small to collect appreciable lymphocytic infiltrates from, or to collect cytokines from (both of which might confirm an autoimmune process). And, generally, the samples are not cultured to reveal if there is a direct viral attack to the nerves (though I imagine this might be doable).

One thing that can be tested for is the presence of amyloid (my samples were--negative). This is an extraordinarily rare situation, though (literally about one in a million).