What you do is gather as much information about the condition as you can and take it with you to the evaluation. Ask the examiner to read about the condition and see how much your symptoms compare with those given for the condition. It's what the condition does to your body or mind that will determine whether you would be approved for disability. I have a condition that, while it is not extremely rare, has been often misdiagnosed (mine was incorrectly diagnosed for decades). I have Charcot-Marie-Tooth disease, which is in the family with Multiple Sclerosis, Muscular Dystrophy, and Lupus. It causes tearing and breaking of tendons and ligaments. Drs. kept trying to say I had Lupus for years. An occupational therapist was the person who finally figured out what I have. If you have something that is obscure, find out everything you can about the condition, print it out, and take it to the person evaluating you. Tell him how it affects your daily living every day. That is the key to getting disability benefits.