There's a rare disorder that turns your muscles into bone!

It's called Fibrodysplasia ossificans progressiva (FOP). It's a really rare disorder that affects between 1 and 2 million people in the world. What it does is it gradually replaces muscle and connective tissue, like joints and ligaments, with bone. The most obvious effect is that it restricts movement.

The process usually starts in early childhood and the first signs of the extra-skeletal bones being formed are with the neck and shoulders. People with this disorder also develop eating and breathing problems due to bone restricting the proper function of these processes. The disorder is genetic in nature and it results from a mutation in a specific gene.

One of the telltale signs of people born with the disorder is their toes and thumbs. People with FOP are generally born with big, malformed toes and short thumbs. Any fall or injury is dangerous because it causes abnormal muscle swelling and makes the bone-turning process even faster.