If your sister has PN and isn't diabetic, that may be very significant. Mine was early onset with cluminess, an inability to run, skate, or jump since childhood, but no pain. I am extremely tall and large boned so very strong which compensated somewhat during my young adult years, raising a big family.

As other have mentioned, first PN symptoms began with numbness in toes which spread upwards, beginning in my 30's, along with balance problems, ankle weakness, and a tendency to trip on curbs, etc. I spent years attributing leg pain and weakness/fatigue to varicose veins, phlebitis, etc. before being sent to a neurologist by my podiatrist. I had developed a seriously infected callous without knowing it and the debridment and cleaning up was done without any anesthetic, I was that insensate. It was already pretty severe. Like Echoes, my numbness is above the kness now.

I would definitely pursue the question of a hereditary neuropathy with your doctor. My own belief is that a lot of idiopathic cases are actually hereditary.
Hope you get more info soon!