Fibrous Dysplasia

Fibrous dysplasia is a developmental condition in which fibroosseous tissue replaces normal marrow within a portion of one (monostotic – 70 to 80%) or more bones (polyostotic). Polyostotic fibrous dysplasia (20 to 30%) involves multiple bones, and may have extensive skeletal involvement. Any bone may be involved, but the hip, proximal femur, tibia, cranial, and facial bones are most common. Although reported incidences vary, craniofacial and jaw involvement occurs in up to 50% of patients with polyostotic disease and in up to 25% of patients with monostotic disease.