What Is Fibrous Dysplasia?

Fibrous dysplasia is a chronic disorder in which bone expands due to abnormal development of fibrous tissue, often resulting in one, or more, of the following:

• Uneven growth of bones
• Pain
• Brittle bones
• Bone deformity

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.

The most commonly affected bones include the following:

• Femur (thighbone)
• Tibia (shin bone)
• Ribs
• Skull
• Facial bones
• Humerus (the bone of the upper arm)
• Pelvis
• Vertebrae in the spine (less often)

Some people develop hormonal problems and a condition called McCune-Albright syndrome. McCune-Albright syndrome, another form of fibrous dysplasia, includes different symptoms, such as early onset of puberty and skin spots, called cafe-au-lait spots.

Fibrous dysplasia usually occurs in children and young adults, and is found equally between males and females.