My brother was a Type 1 diabetic and back in high school I did a report on diabetes. One of the things that struck me was that before 1921, type 1 diabetes was basically 100% fatal. I was wondering what other common ailments have effectively nullified. Other examples are smallpox, polio, and the bubonic plague, but these are all infectious. I was wondering if there were other ailments that a child is born with or later develops that used to be highly fatal, that is now easily treatable?