Only the medical issue is relevant to the employer. e.g. if you have severe epilepsy and the job is graphic design, you probably should mention it somewhere. Maybe not on the C.V., possible on the questionnaire form they give that often asks for relevant medical information but this practice obviously varies. I'm not sure exactly what the story is. Perhaps an employer could comment.
I just have the scenario of a newly hired person saying after they've been accepted, "Oh, by the way, I have severe narcolepsy, I will be falling asleep for 20 minutes every 2 hours, you can't fire me because its a medical condition, maybe I should have told you but you never asked!".
Employer would then slam his face into the desk and scream vulgarities.