Celiac disease is not a disease
The New Oxford American Dictionary defines a disease as:
a disorder of structure or function in a human, animal, or plant, esp. one that produces specific signs or symptoms or that affects a specific location and is not simply a direct result of physical injury
For this discussion, the key point is “a disorder of structure or function.” With celiac disease (CD) however, there is a problem: the person does not have “a disorder of structure or function.” Their structure or function would have been just fine before the agricultural revolution. There is nothing wrong with the person; the problem is the invented diet of the agricultural revolution. (Consider it this way: if someone is suffering from chronic mercury exposure, you do not say they have mercury disease, you say they have mercury poisoning.)