"There is a genetic disease called fibrodisplaysia ossificans progresiva. When tissue is damaged, it is replaced with bone.
Growths form underneath their skin and their joints lock solid So over time those affected slowly become encased in a prison of bone just beneath their own skin.
They usually have to choose between sitting or standing up for the rest of their life. By the end of their life they have to drink every meal through a straw and can barely move"
No offense, (and I sincerely mean that) wikipedia should never be used as a credible source of information. At least, not exclusively.