A 14-year-old girl from Sichuan Province, whose ankles are stiff and whose muscles are turning to bone, has had her problem diagnosed at a Shanghai hospital.

Doctors at Tongji Hospital said yesterday that the girl, Ni Min, suffers from a condition known as fibrodysplasia ossificans progressiva (FOP), or Stone Man Syndrome.

It is an extremely rare disease of the connective tissue and is caused by a genetic mutation. As a result, the body’s repair mechanism causes fibrous tissue like muscle and tendon to be ossified. Injuries can cause joints to become permanently frozen in place.