Fibrodysplasia ossificans progressiva (
FOP) is an extremely rare
connective tissue disease. The disease is caused by a
mutation of the body's repair mechanism, which causes fibrous tissue (including
muscle,
tendon, and
ligament) to be
ossified spontaneously or when damaged. In many cases, injuries can cause
joints to become permanently frozen in place. Surgical removal of the extra bone growths has been shown to cause the body to "repair" the affected area with even more bone.