If you suspect a disease you should have first a diagnose by a doctor through proper tests and exams.
If you have a diagnose then the proper specialist is a Naturopathic Doctor, If Naturopathic Medicine is licensed in your state. If its not, you have to see an MD specialized in Nutrition. Theres Naturopathic Doctors in every state anyways, but if they're not regulated and licensed by the state I wouldnt mess with them anyways for liability reasons.