The disease is found equally in males and females and does not appear to vary in incidence among races. Recent studies indicate that fibrous dysplasia may be caused by a chemical abnormality in a protein in the bone that leads to an overgrowth of bone cells that produce fibrous tissue. The chemical abnormality occurs because of a mutation or change in the structure of the gene that produces the protein. Fibrous dysplasia is thought to be a congenital disorder, meaning that individuals who have it probably had it when they were born. There is no evidence, however, that the disorder can be inherited.
Symptoms Depending on where a patient has fibrous dysplasia, various problems can develop.
Bone pain may occur due to the expanding fibrous tissue in the bone. The onset of pain may signal an impending fracture in a bone that has been weakened by this gradual expansion. A fracture may cause a sudden increase in severe pain. It is also possible, although less common, for abnormal bone to produce pain by pressing on an adjacent nerve. Bone deformity caused by fibrous dysplasia is most obvious when it occurs in the skull and facial bones.