Fibrous dysplasia is an uncommon bone disease that can affect virtually any bone in the body. It is a chronic condition in which scar like tissue develops in place or normal bone. The affected (fibrous) bone gradually grows and expands over a period of years, weakening the bone. It can crack (fracture) the bone and cause the affected bone to deform.
Most people with fibrous dysplasia are diagnosed during adolescence or early adulthood. It accounts for approximately 7% of all benign bone tumours. Bones most commonly affected are the thigh bone (femur), shin bone (tibia), ribs, skulls, upper arm bones (humerus) and pelvis.Most people with this condition have only one bone affected - monostotic fibrous dysplasia, and develop no signs and symptoms. Less often multiple bones are involved – polyototic fibrous dysplasia. This form is generally more severe and can involve as few as 2 bones in the same limb or multiples sites throughout the bone.