The biopsies is for small fiber neuropathy and autonomic neuropathy. When your body has problems controlling body temperature, heart rate and arrhythmias. I have severe axonal sensorimotor peripheral polyneuropathy, small fiber neuropathy, cardiac autonomic neuropathy aka CAN and dysautonomia neuropathy. From small fiber neuropathy down can only be tested by punch biopsies. They take the nerve send it off for testing. It also makes sure you don’t have amyloidosis.