Fibrous dysplasia is an uncommon bone disorder in which scar-like (fibrous) tissue develops in place of normal bone. This irregular tissue can weaken the affected bone and cause it to deform or fracture.
In most cases, fibrous dysplasia occurs at a single site in one bone, but can occur at multiple sites in multiple bones. Single bone involvement usually occurs in adolescents and young adults. People who have more than one affected bone typically develop symptoms before the age of 10.
Although fibrous dysplasia is a genetic disorder, it's caused by a gene mutation that's not passed from parent to child. There's no cure for the disorder. Treatment, which may include surgery, focuses on relieving pain and repairing or stabilizing bones.
Fibrous dysplasia may cause few or no signs and symptoms, particularly if the condition is mild. More severe fibrous dysplasia may cause:
- Bone pain, usually a mild to moderate dull ache
- Bone deformity
- Bone fractures, particularly in the arms or legs
- Curvature of leg bones
Fibrous dysplasia can affect any bone in the body, but the most commonly affected bones include the following:
- Thighbone (femur)
- Shinbone (tibia)
- Upper arm bone (humerus)
Rarely, fibrous dysplasia may be associated with a syndrome that affects the hormone-producing glands of your endocrine system. These abnormalities may include:
- Very early puberty
- Overactive hormone production
- Light brown spots on the skin
Increased bone pain also may be associated with the normal hormonal changes of the menstrual cycle or pregnancy.
When to see a doctor
See your doctor if you or your child develops any of the following:
- Bone pain that increases with weight-bearing activity or doesn't go away with rest
- Bone pain that interrupts sleep
- Difficulty walking or limping
- Unexplained swelling
- Changes in bone shape
- Difference in limb length
Fibrous dysplasia is linked to a gene mutation present in certain cells that produce bone. The mutation results in the production of immature and irregular bone tissue. Most often the irregular bone tissue (lesion) is present at a single site on one bone. Less often multiple bones are affected, and there may be more than one lesion on multiple bones.
A lesion usually stops growing sometime during puberty. However, lesions may grow again during pregnancy.
The gene mutation associated with fibrous dysplasia occurs after conception, in the early stages of fetal development. Therefore, the mutation isn't inherited from your parents, and you can't pass it on to your children.
Severe fibrous dysplasia can cause:
- Bone deformity or fracture. The weakened area of an affected bone can cause the bone to bend. These weakened bones also are more likely to fracture.
- Vision and hearing loss. The nerves to your eyes and ears may be surrounded by affected bone. Severe deformity of facial bones can lead to loss of vision and hearing, but it's a rare complication.
- Arthritis. If leg and pelvic bones are deformed, arthritis may form in the joints of those bones.
- Cancer. Rarely, an affected area of bone can become cancerous. This rare complication usually only affects people who have had prior radiation therapy.