--with documented small fiber neruopathy, especially from metabolic (i.e., diabets, thyroid) or autoimmune causes (which would likely include a lot of "idiopathic" people) have some degree of autonomic dysfunction.

For many people, fortunately, this is fairly limited, even subclinical, and only revealed through specialized testing, such as the sweat test. This occurs as the autonomic fibers are also unmyelinated and fall into the category of "small fiber" (as mentioned, the other "small fiber" nerves subsume the sensation of pain and temperature; some neurologists will refer to these fibers as "free nerve endings").

The most common manifestation of this small scale dysautonomia is blood pressure changes, but sweat disruptions and digestive/eliminative disruptions are also fairly frequent.

http://neuromuscular.wustl.edu/senso...ml#sfpnchronic

http://neuromuscular.wustl.edu/autonomic.html