Fibrous dysplasia is a disorder in which bone expands due to abnormal development of fibrous tissue.
Any bone can be affected. More than one bone can be affected at any one time, and when multiple bones are affected, it is not unusual for them to all be on one side of the body. However, fibrous dysplasia does not spread from one bone to another. Some people develop hormonal problems and a condition called McCune-Albright syndrome, which is a type of skin pigmentation problem. Fibrous dysplasia usually occurs in children and young adults, and occurs equally as often in males and females.