When I moved to college, I met a couple friends who said they had a condition called "Ehlers-Danlos syndrome." I had no idea what that was (or how to properly spell it), but the condition left them with some interesting features. Both of them were incredibly flexible, being able to contort their fingers and shoulders in ways I would never be capable of. Even though super flexibility may sound pretty cool, it comes with its downfalls. On multiple occasions, one of my friends has twisted her knee the wrong way simply while walking down the sidewalk. I suppose it's like a snake's movable jaw; with increased flexibility comes a sacrifice to overall strength.
My friends also showed me that EDS resulted in increased skin sensitivity. One finds shaving her legs to be torturous, and the other has been known to cut himself on the most innocent of objects (from leaves flying by in a gust of wind to the hardened frosting on a cupcake). They may be more sensitive to temperature and pressure on their skin as well.
Although these are common symptoms of Ehlers-Danlos Syndrome, not all people with EDS experience the same effects, and EDS has many different types. I did some research to find out what causes this condition and why it has so many manifestations. It seems that EDS is caused by a defect in the body's collagen proteins and proteins that aid in the construction of collagen. Collagen plays a strong role in connective tissues all over the body, meaning that EDS can lead to weakened joints, difficulty in wound healing, and even weakening of the bicuspid valve in the heart. The collagen protein defects characteristic to EDS have genetic causes, and so the condition may be passed from parents to children or may even be due to spontaneous mutation. Although EDS cannot be "cured," damage to the body may be prevented. For my friends, that may simply mean avoiding a strong high-five and not rough-housing with friends.
Because there are many types of EDS, EDS can result from mutations in a variety of genes. I will not explore all of those here, but if you are interested in learning more about EDS, I encourage you to do a quick search on the internet. There is a lot of information out there about this intriguing condition!
Also, just to throw in a bit about animals, Ehlers-Danlos syndrome is not limited to humans. Other animals including dogs and cattle may get EDS too!