Fibrous dysplasia is an uncommon bone disorder in which scar-like (fibrous) tissue develops in place of normal bone. This can weaken the affected bone and cause it to deform or fracture.
In most cases, fibrous dysplasia affects only a single bone — most commonly the skull or a long bone in the arms or legs. This variety usually occurs in adolescents and young adults. People who have more than one affected bone typically develop symptoms before the age of 10.
Fibrous dysplasia is a genetic disorder and there's no cure. Treatment, which may include surgery, focuses on relieving signs and symptoms.