That is part of the reason they are so difficult to understand. They seem to have a hereditary factor as well, except the type of autoimmune disease can vary in the same family, with a grandmother having had diabetes and the daughter having Lupus and the granddaughter developing Rhematoid Arthritis. Diagnosis is based on symptoms presenting, physical examination and lab tests. There is not one specific blood test for the diseases, however in most cases the person will have a positive ANA, antinuclear antibody, for one. It is difficult to diagnose many of these disease, especially in the early stages of disesase.
Treatment varies with each disease and with each patient.
With endocrine type diseases such as diabetes or thyroiditis, hormone replacement therapy is used. For inflammatory processes and pain, often steroids or other anti-inflammatory drugs are used, among others. Every case is individualized. Because the diseases are chronic, meaning there are no cures, they are lifelong, the doctors can only treat the symptoms. Unfortunately, autoimmune diseases remain the most poorly understood types of illnesses, as we mentioned previously.