A young girl I know, a quite young child at the time, submitted her DNA in the very beginning of 23andme. When there are genetic issues 23andme will actually call you and recommend you see a doctor. This young girl had XY chromosomes, it’s called Swyer syndrome, despite being in every way phenotypically a girl. People with this condition have to have their sex organs removed and go on hormone therapy. I know the family well but I’m not one to be super nosy about the specifics here: apparently some sort of concerning tumor had been found during surgery and now the girl has to get scans every once in a while. The parents say if they hadn’t done the testing, it’s likely she would have died. The condition itself is not life threatening but there are increased risks of getting tumors because of it from what I understand.