Recurrent episodes of demyelination and remyelination of peripheral nerves lead to the concentric proliferation of Schwann cells around axons, also known as “onion bulb” formations. This is typically seen with inherited dysmyelinating disorders (CMT1A, HNPP) and CIDP. Congo red staining of the endoneurium and blood vessel walls can be seen secondary to amyloid deposition. Thickened blood vessels with basement membrane reduplication can be seen with diabetic neuropathy. Macrophage-mediated demyelination can be seen with AIDP.