--may be going on here; none of us are exempted from being co-morbid.

First, those vitamin levels bear closer scrutiny. The 400-500 level of B12 is really only a low normal, if that; many of the new ranges used in Europe and Japan start at the 500-550 level. Given this, and the low normal D and folate levels, a search for malabsorption syndromes is in order, particularly celiac. I know you've had an investigation for this, but sometimes the damage is patchy and incomplete, especially early in the process, and a diagnosis often depends on the number of biopsies taken for sample--there was recently an article on how part of the underdiagnosis of celiac may relate to insufficient numbers of samples taken, as well as a low rate of samples during upper endoscopy:

http://www.huffingtonpost.com/2012/0...n_1643914.html

Also see this section from the Gluten File:

https://sites.google.com/site/jccglu...testsandbiopsy

And, your neuropathy pattern is not uncommon in the case of gluten sensitivity/celiac--the condition is know for producing non length dependent neuropathies and at times for an autoimmune attack on the dorsal root ganglia, which, generally, results in sensory symptoms rather than motor:

https://sites.google.com/site/jccglu...ationsofgluten


Of course, there can be NON-celiac/NON-gluten autoimmune attacks on the dorsal root ganglia that may lead to similar sensory/autonomic symptoms. Sjogren's syndrome is one culprit, and there are others (in some cases, the cause is never found):

http://neuromuscular.wustl.edu/antibody/sneuron.html

AND--it's entirely possible this may have, ultimately, an infectious cause. Lyme infection can present this way, as can other infectious causes (particularly insect borne, such as West Nile):

http://neuromuscular.wustl.edu/nother/infect.htm#cmv

I admit, this can be a very difficult puzzle to pull together.