I rescued this plant a couple of months ago. It's this disease or damage?

My thought would be damage of some kind. The problem is that the central growth point appears damaged beyond repair, so the plant will have to generate a new growth point or points. If the visual damage is static and not growing, whatever caused the damage is probably in the past. If it is continuing, then I could well be wrong and it's a disease of some kind. Due the appearance in the center, I'd think the plant is vulnerable to disease as it's seen in the photo. If it were mine, I'd try to protect the center from getting too much moisture. I'd guess the plant will put out new growth if the stem is solid and healthy and the plant is getting sufficient light and air circulation. Just my opinion.

I agree about the growth center being lost, and that being a bigger concern perhaps than the leaf damage. If that were my plant I would just toss it and move on, between the one problem and the other. I do not recognize the leaf problem at all, but if you see it on any growth from here on out, seriously consider tossing the plant (unless you determine what the issue might be, by that point).