I also find fatigue to be worst and most disabling symptom to appear with my SFN. However my neurologist, a Mayo trained specialist in SFN states that Fatigue is NOT a symptom of SFN. That has left us hunting for another reason for the Fatigue. However we haven't gotten very far even with extensive testing. Her differential is auto-immune and she rightly states there are so many auto-immune disorders that have yet to be explored.
One rare disorder that fits PN and fatigue is Fabry's disease.
Please let me know of any other thoughts on this.