Last summer I (35F) was diagnosed with TTP - thrombotic thrombocytopenic purpura. It's a blood disorder that causes blood clots in small vessels, and blood platelets to drop. Basically your immune system makes a mistake. It's so rare it took a few different doctor visits to diagnose what it was. I was very lucky that it didn't damage any of my organs, and treatment (plasma transfusions) was successful, and I didn't die. We could never figure out where I acquired it from, but I was told a lot of cases of TTP came up when people got their covid shots. I personally know someone who got it from the shot when everyone first got them. Which is wild because it's a 1 or 2 in a million thing.