Swelling on a 10 year old girl's temple due to underlying fibrous dysplasia of the skull. This is an extremely rare developmental abnormality with no known cause, which results in solid bone being replaced with weaker fibrous material. Symptoms include aching and tender bones, and a tendency to fracture easily. It can be monostotic (affects only one bone, known as Jaffe-Lichtenstein disease) or polyostotic (affecting several bones independently), with the most severe form being known as Albright Syndrome.