I have Marfan's Syndrome. The genes which code for fibrillin, a structural protein found just about everywhere in the body, in my case code for a defective form of the molecule. Fibrillin is a huge molecule, with several thousand atoms, that can be defective in hundreds of ways. Relevant to this topic, it has weakened the discs, ligaments and vertebrae in my lower spine, pinching and irritating the nerves which manage continence. It also gives me sciatica periodically. I have a very mild form of the disease; the worst cases of it can kill folks before their twentieth birthday.