Since I happen to be one of the many who have dysautonomia, I thought it worth a few minutes to post this (graphic thanks to a fellow sufferer).
What on earth is dysautonomia? It's an autonomic nervous system gone awry. Which is not a good thing. Your autonomic nervous system controls all kinds of automatic functions, like heartbeat, blood pressure, sweating. As you can see in the graphic, there are a variety of maladies all under the Dysautonomia umbrella.
I don't even know for sure which variety I am. I do know that I have a dramatic drop in blood pressure when I move from lying down to sitting or sitting to standing. I become completely exhausted from short shopping trips, and I suffer from exercise intolerance, which basically means I don't recover normally from exercise - something seemingly easy and brief and sometimes leave me recovering on the couch for days. And yet exercise is important. It leaves us in a "damned if you do and damned if you don't" conundrum.
Many people who have dysautonomia faint. I'm lucky in that I've never fainted. I get "grey outs" instead of "black outs" - it effects my vision, and I know what's happening, so I compensate by sitting back down, or dropping into a crouch.
There is medication that helps the low blood pressure, at least for some people. It works fairly well for me, for which I am grateful. Sometimes when a younger person has dysautonomia, it is a temporary thing, but for many it is a condition they have to learn to live with the rest of their lives. There is no cure, and it can cause very serious consequences or only mild ones. The causes are myriad, so patients often spend a lot of time and money trying to figure it all out.
If you want to learn more, this site is a good resource: http://www.dinet.org
Patti