I have two odd medical conditions and neither has any noticeable effect on me. I'm not a doctor so excuse me if I make a mistake on the explanation and feel free to correct me.

One I have permanent nystagmus in both eyes. Basically a twitch in your eye when you look really hard to the side. Normally people get this when they're on depressants like alcohol. It's one of the things cops check for on DWIs. I have it all the time. The best explanation the doctors could come up with was a lingering symptom from a serious concussion I had in high a cheek where I lost vision in my left eye for a few hours.

The second is a Brachial Branch Block. Which means the one chamber of my heart doesn't get the signal to fire from the nerves attached to it. Instead it gets a delayed signal to fire from the nerves controlling the other side of my heart. So one of the chambers is lagging hard.

Supposedly neither thing really affects me, but they're both reasonably rare conditions to have without other health problems.