Why Does FOP Turn People's Bodies to Bone?

Fibrodysplasia ossificans progressiva, also known as FOP, is a rare disease which turns muscle and connective tissue into bone that forms outside the skeleton. Over the years, Inside Edition has met with many people who have this rare illness to see what their lives are like and how they come together at events like annual conventions to help each other heal. Here is a glimpse inside the world these brave people face.