Fibrous dysplasia

Fibrous dysplasia is a condition that causes abnormal growth or swelling of bone. The affected bone becomes enlarged, brittle and warped. It can occur in any part of the skeleton, but the bones of the skull and face, thigh, shin, ribs, upper arm and pelvis are most commonly affected.

This rare disorder is usually diagnosed in childhood or early adulthood and may affect one or several bones. Males and females are equally affected. Fibrous dysplasia is not a form of cancer and does not increase a person’s susceptibility to cancer. In some cases, hormone problems and changes in skin colour also occur.

Fibrous dysplasia cannot be cured, but it can be managed with medical treatment.

Symptoms of fibrous dysplasia#

In some cases, fibrous dysplasia causes no symptoms and is only found by chance during investigations for an unrelated problem.

When symptoms do occur, they can include:

• An increased tendency to bone fractures.
• An unusual gait - for example, a “waddle” or rocking from side to side when walking.
• Pain, caused by the expansion of bone or by the pressure of expanding bone against a nerve.
• Irregular bone growth and bone deformity.

Eyesight problems or other sensory problems may develop if the bones of the skull are affected.

Complications#

Fibrous dysplasia can lead to a range of complications. These may include rickets, and if the pelvis and leg bones are affected, an increased risk of arthritis.

Types of fibrous dysplasia#

The main types are:

• Monostotic fibrous dysplasia - only one bone is affected. This accounts for about seven cases in every 10, and the skull is the most commonly affected site.
• Polyostotic fibrous dysplasia - two or more bones are affected.
• McCune-Albright syndrome - fibrous dysplasia is associated with hormone disturbances and skin pigment changes.

About one case of fibrous dysplasia in every 10 is diagnosed as McCune-Albright syndrome. People who have fibrous dysplasia in more than one bone are at increased risk of developing it.

Symptoms of McCune-Albright syndrome may include darkened patches on the skin (café-au-lait spots), the onset of puberty before 10 years of age, an overactive pituitary gland (which could lead to abnormal height) and an overactive thyroid gland (hyperthyroidism).

Causes of fibrous dysplasia#

Fibrous dysplasia is caused by a change in the GNAS1 gene that makes the gene more active than usual.

This gene change is not inherited from the parents and is not present at conception. It arises during an early cell division in the developing embryo. As a result, the change is present in only some cells of the body, and its effects may be confined to a single location. The same underlying mechanism causes McCune-Albright syndrome, but in that condition the effects are more widespread.

Diagnosis#

Sometimes the symptoms of fibrous dysplasia mimic those of other conditions. For example, fibrous dysplasia of the vertebrae (backbones) may be mistaken for idiopathic scoliosis.

Fibrous dysplasia is diagnosed using a number of tests, which may include:

• Medical history and physical examination.
• Blood tests.
• X-ray examinations.
• CT scan.
• Bone biopsy (a small sample of bone is collected for examination in a laboratory).

Treatment#

Treatment depends on your age, general health and the severity of the condition. It may include:

• Treatment to reduce the risk of complications such as rickets or fractures.
• Medication to strengthen bones, such as medicines commonly used to treat osteoporosis.
• Pain management therapy.
• Physiotherapy to improve joint mobility.
• Treatment for hormone imbalances and other problems.

Surgery#

Surgery is recommended for painful or fractured bones, or when joints can no longer move freely. It is also used when fibrous dysplasia causes complications such as pressure against the brain, spinal cord or nerves.

Usually, the section of diseased bone is removed and the remaining bone is strengthened with grafts of healthy bone taken from unaffected parts of the skeleton. In some cases, pins, rods or other permanent devices may be inserted to further support the bone.

Surgery may successfully treat the condition when only one bone is affected. If several bones are affected, it may not be possible to remove every section of diseased tissue.

Your treatment team#

Specialist doctors in your treatment team may include:

• An orthopaedic surgeon to treat bone problems.
• A plastic surgeon to treat facial deformities.
• A neurosurgeon to treat complications of the central nervous system (brain and spinal cord).
• An endocrinologist to treat hormone imbalances in the case of McCune-Albright syndrome.

Exercise#

Regular weight-bearing exercise helps to strengthen bone, increase joint mobility and maintain a healthy weight. Because people with fibrous dysplasia are at increased risk of fractures, it is important to develop an appropriate and safe exercise program with guidance from your treatment team.

Support#

If you or a family member has been diagnosed with fibrous dysplasia, it may help to speak to a genetic counsellor.

Genetic counsellors are health professionals qualified in both counselling and genetics. As well as providing emotional support, they can help you understand the condition, what causes it, and what a diagnosis means for your or your child’s health and development and for your family. They are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.

Key points#

• Fibrous dysplasia is a condition that causes abnormal growth or swelling of bone.
• Fibrous dysplasia cannot be cured but can be managed with medical treatment.
• When symptoms occur, they can include an increased tendency to bone fractures.
• Fibrous dysplasia can cause a range of complications.
• The main types are monostotic (one bone), polyostotic (two or more bones) and McCune-Albright syndrome.

Where to get help#