--have neuropathy as a a secondary component; most of the anti-nuclear antibody (ANA) autoimmunities can cause it, as can rheumatoid arthritis, and there are also a whole lot of less well-known conditions in which the autoimmune attack is directly on components of peripheral nerve.

The best summarizing database I know that describes this is the Washington University (St. Louis) neuromuscular website:

Immune Neuropathies: Axonal

(This is just the ANA-immune mediated section, since you mentioned rheumatoid arthritis--you can explore the rest of the website for very wide-ranging information about a host of neurologic conditions.)

As far as the B12 goes, that level may have been quite normal depending on how much you were supplementing with and whether you continued to do so right up to the time of the testing. My B12 levels are often in that area and I have to explain to doctors that I do take B12 every day.