Fibrous Dysplasia

What is fibrous dysplasia (FD)?

Fibrous dysplasia (FD) is an uncommon disorder of the skeleton that is rarely cancerous (less than 1 percent). This disorder results in fibrous bone-like tissue that replaces normal, healthy bone, causing the affected areas to be more susceptible to fractures (broken bone).

FD can affect one bone (known as monostotic FD), multiple bones (known as polyostotic FD) or the entire skeleton (known as panostotic FD). It may also be associated with darkened patches of the skin known as café au lait macules. Most often, it affects the bones of the legs, upper arms, skull (including the facial bones) and ribs.

Who is likely to have fibrous dysplasia (FD)?

Anyone can have fibrous dysplasia, and it can be diagnosed at any age. The condition is not linked to any one ethnicity or geographical location, and affects males and females equally. It is believed that the bone abnormality occurs in childhood, but may go unnoticed unless there is associated pain, a limp develops or a fracture occurs.

How common is fibrous dysplasia (FD)?

Fibrous dysplasia is rare. And because mild cases may go undiagnosed, it is difficult to define the true frequency of this disorder.

What causes fibrous dysplasia (FD)?

Fibrous dysplasia results from a genetic mutation (change) on chromosome 20. This mutation happens on one gene that directs bone formation and growth, but what causes this mutation to occur remains unknown.

What are the symptoms of fibrous dysplasia (FD)?

The symptoms of fibrous dysplasia vary greatly depending on:

• How many bones are affected
• Location in the body of the affected bones
• Whether any injuries, like fractures, have occurred

People living with fibrous dysplasia may have no signs or symptoms at all, but for others living with FD signs and symptoms may include:

• Fatigue, particularly in young children
• Pain and weakness in the areas affected
• Fractures or breaks
• Misshapen bones (bone deformity)
• Cafe au lait spots
• Signs and symptoms of underlying endocrine disorders such as growth hormone excess, overactive thyroid and early puberty

Because FD can affect any bone in the body, symptoms may range from mild to severe. Some symptoms may seem unrelated to the bones, such as:

• Nasal congestion, uneven jaws or bulging eyes if bones in the face are affected
• Vision loss or hearing impairment if specific nerves become compressed due to the fibrous bone tissue

In rare cases, fibrous dysplasia occurs as part of a group of conditions known as McCune-Albright syndrome. This syndrome affects the bones, endocrine (hormone-producing) tissues and skin.

How is fibrous dysplasia (FD) diagnosed?

FD is diagnosed by physicians with expertise in metabolic bone diseases. A physical exam, X-rays or other imaging, and blood or other tests may be used.

How is fibrous dysplasia (FD) treated?

Treatment for fibrous dysplasia depends on the severity of the disorder and the presence of symptoms. In some cases, doctors simply monitor your bone health to make sure FD does not get worse.

Doctors frequently prescribe medications called bisphosphonates in an effort to ease pain and help prevent fractures. Studies are ongoing to determine the effectiveness of denosumab (Prolia®), which is a drug commonly used to treat osteoporosis. For some people, braces can help prevent bone fractures.

Surgery may become necessary if a bone affected by FD breaks. Surgery can stabilize the bone, correct disfigurement and prevent further fractures. Sometimes doctors use metal plates, rods or screws to stabilize the bones. Contouring or “shaving” affected bone can result in rapid regrowth.

What complications are associated with fibrous dysplasia (FD)?

Growth of fibrotic bone can result in nerve compression and result in complications like nasal congestion, vision loss, or hearing impairment.

Can fibrous dysplasia (FD) be prevented?

There is no way to prevent fibrous dysplasia because FD is a genetic mutation of unknown origin (see Overview).

What is the prognosis (outlook) for people with fibrous dysplasia (FD)?

Individuals with milder forms of FD often live normal, otherwise healthy lives. The prognosis is as widely variable as the disorder itself, and is based on the bones affected, whether other structures such as nerves are affected, and whether fractures occur.

Fibrous dysplasia can affect many bones in the body, but once it has established in the skeleton, it doesn’t spread.

When should I call my doctor if I think I have symptoms of fibrous dysplasia (FD)?

If you notice any signs or symptoms of fibrous dysplasia, contact your pediatrician or primary care physician for an evaluation.

What questions should I ask my doctor?

If you have fibrous dysplasia, you may have many questions for your doctor, including:

• How can I keep my bones as healthy as possible?
• How should my bone health be monitored to avoid potential complications?