Say you get your DNA sequenced, say they even find a segment that seems "off" from other DNA sequences.
What the heck would you do about it? We don't understand DNA and protein folding enough to actually take the output of DNA sequencing and give you something to change that. We don't have a comprehensive view of the human body or biology or DNA to do anything with it. There's not really going to be much in the way of treatment for a single instance of a random negative mutation.
Approximately 20% of rare diseases get diagnosis in my lab. Note these are usually very extreme cases where the people are quite sick. More common genetic diseases are picked up by routine clinical genetics which don’t reach me. Interestingly some of the hardest illnesses to detect are those which are common but no known mechanism - since they are common they are hard to detect statistically.
If you have a genetic diagnosis you are more likely to get medical care targeting the root cause instead of treatments that can only treat the general symptoms - like anti inflammatory drug, etc. In rare cases people may get transfusions to replace their protein deficiency, etc.
You can find solace in knowing what's wrong with you and track studies for your particular gene that's off. It's not a given that your autoimmune disease wasn't at least studied at one point, knowing what the markers are and whether you have them could help track down whatever knowledge exists.
They may be able to tell things like "You are a rapid metabolizer of drug XYZ" or "You are a poor metabolizer of drug ABC". Knowing that they may be able to try more effective therapies for you that they wouldn't normally have thought of.
What the heck would you do about it? We don't understand DNA and protein folding enough to actually take the output of DNA sequencing and give you something to change that. We don't have a comprehensive view of the human body or biology or DNA to do anything with it. There's not really going to be much in the way of treatment for a single instance of a random negative mutation.