I kept mine a secret at two of my jobs specifically (as well as the rest), because I know that I could have been fired. I know they say you can't be fired for medical conditions that don't impact your work and I would check the fine print if you have a contract. For me, you could twist my si/scars in a way that would make me eligable for dimisal. It's a tricky situation, as well as many mental health issues.