--is rare, but not unheard of. It certainly happened to me.

Generally, it is considered a variant of Guillain Barre syndrome, and often suspected to be caused by a similar process--autoimmune molecular mimicry. The body reacts to some pathogen with an immune response, and may often succeed in destroying the pathogen, but the pathogen turns out to have a very similar molecular configuration to some component of peripheral nerve (much of the body's immune response is mediated by molecular shape), and the now activated immune system attacks anything with a similar configuration as it cannot distinguish the nerve from the original pathogen.

In classic Guillain Barre, the attack is directed at components of the myelin sheathing of the larger nerves, so people get motor, sensory and often autonomic symptoms. In the small fiber variant, the attack is against the components of the nerve itself, as small fibers have no such sheathing; since small fibers are sensory and autonomic, there are typically no motor symptoms (mine were all sensory). Also, since the attack was to nerves too small to be measured by standard nerve conduction studies, it took skin biopsy to confirm there was damage to the smaller nerves.

The Washington University Neuromuscular website has good info on this:

http://neuromuscular.wustl.edu/sensory-small.html

http://neuromuscular.wustl.edu/senso...tml#idiopathic

http://neuromuscular.wustl.edu/antibody/gbs.htm#sens