What is fibrous dysplasia?Fibrous dysplasia is a skeletal developmental anomaly of the bone-forming mesenchyme that manifests as a defect in osteoblastic differentiation and maturation. Virtually any bone in the body can be affected. It is a nonhereditary disorder of unknown cause. Fibrous dysplasia is characterized by uneven growth, pain, brittleness, and deformity of the affected bones. This disorder may involve a single bone (monostotic fibrous dysplasia or Jaffe-Lichtenstein disease) or may affect multiple
bones (polyostotic fibrous dysplasia). The abnormality will cause uneven growth, brittleness and deformity in affected bones. Some patients have only one bone affected (monostotic), whereas other patients have numerous bones affected (polyostotic). While any bone can be affected by fibrous dysplasia, the most common sites of the disease are the femur (thigh bone), tibia (shin bone), ribs, skull, facial bones, humerus (upper arm), and pelvis. The vertebrae are less frequently involved. Although many bones can be affected at once, fibrous dysplasia is not a disease that spreads from one bone to another. Multiple affected bones are often found on one side of the
Fibrous dysplasia is usually evident during childhood, and the bone lesions usually stop developing at puberty. These lesions may be painful, deforming and widespread. The bones most often affected are the ribs, skull, facial bones, thigh bone (femur), shin bone (tibia), upper arm (humerous), and pelvis. Occasionally, the bones in the spine (vertebrae) are affected. Some, but not all, affected individuals experience repeated bone fractures. The exact cause of fibrous dysplasia is not known. Fibrous dysplasia is a very uncommon disorder, and the total number of cases is not known. It is usually diagnosed in children and young adults. If the disease involves more than one bone, it is more likely to produce problems before age 10. The disease is found equally in males and females and does not appear to vary in incidence among races.