not all auto immune diseases can be diagnosed.. especially rare ones... alot of dermatologist and immunologist believe many skin conditions are infact an auto immune disease.. many medications work for different diseases and in many cases they dont actually know why it works for certain diseases it just works!!! thats the beauty of the medical world sometimes there just insnt any understanding. im wanting to try imuran simply becasue if i see great results like patrick it will narrow it down for me personally.. its a immunosuppresent so if it slow down to a hault it would suggest it could be auto immune disease or exzma. thats of course all in my opinion.. like i said before some medicines work and there simply is no answer why they do... lots of drugs actually state that the cause of improvement is unknow.