Abnormal bone structure Fibrous dysplasia of bone 2010-04-21T06:27:42Z Osteitis fibrosa disseminata Fibrous dysplasia of the bones Tumor-like growths that consist of replacement of the medullary bone with fibrous tissue, causing the expansion and weakening of the areas of bone involved. Especially when involving the skull or facial bones, the lesions can cause externally visible deformities. The skull is often, but not necessarily, affected, and any other bone or bones may be involved. Fibrous dysplasia can either effect isolated bones (Monostotic fibrous dysplasia) or also generalized all bones of the body (Polyostotic fibrous dysplasia). replacement of normal bone with abnormal, structurally unsound fibro-osseous tissue, with concomitant obliteration of the hematopoietic bone marrow. The fibrous tissue is rich in fibroblast-like cells that express markers of early stages of osteogenic maturation HP:0010734