My 17 year old son for the past 7 months now has had this white patchy thing inside his mouth on his cheeks and sometimes gums. Its not thrush it has been tested 2 times and had a biopsy and all it said was hyperkaratosis. Its not cheek biting as some may say its in areas you just can not bite including gums. It doesnt scrape off easy and it doesnt hurt, there are no blisters or sores. He does have several autoimmune disease sch as hashimotos, type 1 diabetes and addisons disease. Its not related to any of those. Hes also for the past couple months developed high blood pressure and bad headaches not from the high blood pressure. Im adding a link that has a pic so you can see it. If you have any ideas please let me know. Drs are baffled and so are we. 

https://www.facebook.com/photo.php?fbid=313517842081727&set=a.204833499616829.34164.146881025412077&type=3&theater