<Tr> <Th> Specialty </Th> <Td> Medical genetics </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> 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 . </P> <P> For unknown reasons, children born with FOP have deformed big toes, possibly missing a joint or simply presenting with a notable lump at the minor joint . The first "flare - up" that leads to the formation of FOP bones usually occurs before the age of 10 . The bone growth progresses from the top downward, just as bones grow in fetuses . A child with FOP will typically develop bones starting at the neck, then on the shoulders, arms, chest area and finally on the feet . </P>

What is the disease that turns muscle into bone