They didn't do a proper work up at Mayo. There are tests that can be done to see if your immune system is working. T @ B lymphocytes for example. These are the cells responsible for fighting off infections. In my case, I have all I need but they are attacking me as a foreign object. The fight to flight response is involved as well. I guess my cells get confused like I do. This test should be done for you to help determine if you have an underlying auto immune disorder. A punch biopsy for PN is done too. I can't tell you how many tests I had, I just know it was four days of intensive, doctor to doctor. Ask about specific test you are having done. Look them up so you know what they are doing to you. Do you have a copy of any they did at Mayo? ginnie