--that are often labelled "idiopathic", my sense is that there are a number of hereditary genetic conditions that are yet to be described that cause some of them, but more are likely caused by as yet undocumented autoimmune mechanisms, and a number are likely the result of metabolic dysregulation (i.e., vascular damage caused by blood sugar problems that have not yet progressed to "frank" diabetes).

There are certainly others that are caused by nutritional deficiencies and toxic exposures, and the latter may be more common than we think.

The problem is that many doctors do not do really extensive investigations for these causes. And certainly, many have compressive neuropathies due to spinal or hip or other issues that can be exacerbated by systemic effects in the so called "double crush phenomenon", in which the symptoms are greater than the sum of the parts that contribute to them.

I, for example, have localized pundendal neuropathy in the pelvis that is certainly compressive in nature, given how dependent it is on position and how long I've spent sitting, bending, etc.; it waxes and wanes and returns in bouts. But it would likely not be anywhere near as annoying if I didn't have a systemic idiopathic (though probably autoimmune) neuropathy problem overlaying it since 2003.