Ah! I wrote a bunch back in April and I’m going to refer you back to these posts.
https://connect.mayoclinic.org/discussion/undifferentiated-connective-tissue-disease/
UCTD is an autoimmune disorder where you have signs and symptoms of other “defined” connective tissue diseases, but not enough signs or symptoms to be diagnosed with one of those. So we’re this rag-tag group of people with “autoimmune-y” symptoms that just don’t fit a different category. Our symptoms aren’t the same, and most of us don’t get severe organ damage (because then we’d get diagnosed with something else, ha!), but when studies finally looked at quality of life, not surprisingly it was… not good. Maybe all the uncertainty about what’s wrong with us and whether we will get better or worse and whether we will wake up feeling good or bad or in between- kind of the nature of living with an autoimmune disorder.