I have had small fiber neuropathy for 31/2 years now. I don't know the reason for it and it progressed very quickly. I hope you have success in finding the reason. I searched for a long time. Just recently, after being tested for everything they could think of and being misdiagnosed a few times, I have decided to focus on making me feel better. Although I still hold out hope, I also realize that I may never know the reason. Good Luck