My grandfather suffered from Dupruytren's Contracture. He had to have surgery I think, but it kept growing back.
The palm of his hand was all lumpy, like the tendons underneath it were thicker than they should be (and that, in fact is what happens with this disease).
He had less use of it, I think, because his fingers were being slowly pulled down towards his palm and he couldn't straighten them.
I don't think it hurt him though. I was kind of fascinated by it as a child, so I asked him a bunch of inappropriate questions about it, but I don't think he minded.
I hope I don't have the gene for it. Although, I think they have developed a medication that stops it from happening now.