My dermatologist had me get a biopsy for the itch rash. She indicated that the cause was internal, looking at the dozen or so prescription meds I take. No obvious culprits. I still think the cause may have psychological roots.
Biopsy.
many doctors visits, for a few years. Finally on the 7th biopsy, PN was diagnosed
Biopsy, lots of different meds tried before and after, finally after 3 years or so was labeled PN.
Biopsy by my dermatologist
My family doctor had no idea what it was