Is this a medical condition from birth, or recently developed? Are you asking because you think it will really help your friend if they know someone else knows, or because you just want them to know you figured it out?
A few years ago, I became friendly with a coworker and suspected she had a somewhat rare congenital condition–nothing I could have done anything about, but was curious to know how she handled it. But it wasn’t the kind of thing you could just say, hey, do you have such-and-such? Even though that was what I was itching to do. B”H i controlled myself. She was kind of in denial about it. Eventually, after a while, when we had become pretty close friends, she opened up about it herself, which seemed to help her deal with it.
Given time and space and friendship, if your friend wants to tell you, maybe s/he will.