There is so much that we don't understand about certain diseases. Doctors and scientists are working around the clock, trying to understand Lyme disease, fibromyalgia, and even chronic migraines. Traditional testing provides little insight into these conditions, and few tests exist to "prove" individuals have illnesses like these. Even if a doctor diagnoses your disease, you will still have difficulty getting your disability claim approved.
The insurance company routinely rejects disability claims for conditions like fibromyalgia. Often, the disability insurance company requires "objective medical evidence" of your condition. Obtaining objective proof of your condition is all but impossible for some diseases. Even if there is some test to show a person has fibromyalgia, the disability company may reject the conclusion under the vague definition of objective medical evidence.
The insurance company may accept that the doctor correctly diagnosed your illness, but still reject your disability claim. One would think the opinion of a physician would be enough for the insurance company, but the insurance company has their own doctors who are all too willing to reject your diagnosis without meeting or evaluating you.
Even if you are willing to play their game, you will find the standard of "objective medical evidence" is not fixed. The insurance company's definition of medical evidence is constantly shifting because there is nothing written in your contract to define what objective medical evidence is for your condition specifically. That is why hiring an attorney for your long-term disability case is sometimes necessary.
If your claim was denied because your illness lacks objective medical evidence, and your doctors support your claim, bring your denial letter to an ERISA long-term disability attorney to learn what you can do to appeal the decision.