Fibrous Dysplasia

Fibrous dysplasia is a very rare, non-hereditary genetic disorder in which normal bone and marrow are replaced with fibrous tissue, leaving the bone weak and prone to expansion. Most complications come from fracture, deformity, functional impairment, pain and nerve impingement, and the disease ranges from mostly symptomless incidental lesions to severe disabling disease, affecting one bone, several bones or, rarely, all of them. It is not itself a cancer, but in severe cases it can undergo malignant transformation into cancers such as osteosarcoma or chondrosarcoma, which is why some clinicians treat it as precancerous rather than benign.