What Is Fibrous Dysplasia?
Fibrous dysplasia (FD) is an uncommon bone disease that can affect any bone in the body. The severity of the disease covers a wide spectrum. It can affect a single bone and go unnoticed for years, or it can affect virtually every bone, start very early in life, and result in significant physical impairment. It is caused by defective gene in the cells that form bone. The cause of the gene defect is unknown, but the defect is neither inherited from the person’s parents, nor passed on to the person’s children. When the long bones (the bones of the legs and arms) or flat bones (ribs and pelvis) are affected, the bones weaken, may bow, are often painful, and will frequently fracture. Affected bones in the skull often expand, may cause disfigurement and, again, are often painful.
Most people with fibrous dysplasia are diagnosed during adolescence or early adulthood. Mild cases usually cause no signs or symptoms. More-serious cases of fibrous dysplasia may result in bone pain and deformity. The basic cause of fibrous dysplasia is unknown. There’s no cure for fibrous dysplasia. Treatment focuses on relieving signs and symptoms.
Different types of fibrous dysplasia
The main types of fibrous dysplasia include:
1) Monostotic fibrous dysplasia – only one bone is affected. This accounts for about seven cases out of every 10. The most commonly affected site in monostotic fibrous dysplasia is the skull.
2) Polyostotic fibrous dysplasia – two or more bones are affected.
3) McCune-Albright syndrome – fibrous dysplasia can be associated with hormone disturbances and skin pigment changes. About one case of fibrous dysplasia in every 10 is diagnosed as McCune-Albright syndrome.
Who Is Affected?
Fibrous dysplasia is an uncommon disorder. It is usually diagnosed in children and young adults, and is present throughout life. The likelihood of getting the disease does not appear to be influenced by gender, race, ethnic background, geographic location, or by any environmental exposures.
What Is the Cause?
Fibrous dysplasia is caused by a defective gene in the cells that form bone and other affected tissues. The defect occurs at some point after conception, most likely early in fetal development. This means that the disorder is not inherited from an affected person’s parents, nor can an affected person with the condition pass it on to his or her children.
What Are the Symptoms?
The most common symptoms of the disorder are painful, misshapen, and/or broken bones (fractures). Fractures are more common between the ages of 6 and 10, but often persist into adulthood. The problems a person experiences depend on which bones are affected. For example, the legs can be of different lengths, leading to a limp and the need for a shoe lift. The bones of the sinuses can be affected, leading to chronic sinus congestion. Only very rarely do serious problems such as vision loss or cancer occur.
What bones are most affected by Fibrous Dysplasia?
Any bone can be affected by Fibrous Dysplasia. Patients with only one bone site involved are diagnosed as having Monostotic FD while patients with numerous affected bones are diagnosed as having Polyostotic FD. This topic was explored as part of the analysis of the FDSOL database performed in the year 2000. Those registering with Polyostotic FD (or MAS) did not have an opportunity to indicate all their affected bone sites when registering, so the study focused on all members who had registered as being diagnosed with Monostotic FD only.The distribution of bone sites for the 318 members with Monostotic FD is as follows:
- Craniofacial (Head: skull/mandible/facial bones): 46%
- Lower limbs (legs/hips/pelvis): 45%
- Upper limbs (arm, hand): 6%
- Axial skeleton (ribs/spine/clavical): 3%
An interesting finding from the analysis is that patients diagnosed with Monostotic FD were as likely to have the effected bone site in the skull (46%) as with all other bones in the body combined (54%). This appears to be somewhat significant since the skull contains only 29 of the body’s 206 bones and is a proportionately smaller bone mass when compared to the rest of the skeleton. There did not appear to be any difference in the reported bone sites between men and women with Monostotic FD.
How Is the Disorder Diagnosed?
The bones in people with fibrous dysplasia have a characteristic appearance on x rays, which is usually sufficient to make the diagnosis. In some cases, a doctor may need to obtain a small bone specimen (a biopsy) to confirm the diagnosis. The usefulness of gene testing is not clear. Since the mutated gene is only present in fibrous dysplasia tissues, it is best to test only the DNA from affected tissue, but even then, doctors do not know with certainty how useful such a test is.
How Is Fibrous Dysplasia Treated?
There is no cure for fibrous dysplasia. Like most medical conditions, one treats the symptoms or problems as they arise. Fractures often require surgery, but can sometimes be treated with just a cast. Surgeries are recommended if a fracture is likely to occur, or in an effort to correct the shape of the bone. Surgery may also be indicated to relieve bone pain. Medications known as bisphosphonates—approved by the U.S. Food and Drug Administration for the treatment of other bone diseases—have been shown to reduce pain associated with the disease. Bone-healthy strategies such as physical activity (with physician approval), and adequate calcium, phosphorus, and vitamin D intake are also important.
Where to get help for treatments?
Treatment depends on the patient’s age, general health and severity of the condition. Specialist doctors may include:
– Orthopaedic surgeon – to treat bone problems.
– Plastic surgeon – to treat facial deformities.
– Neurosurgeon – to treat complications of the central nervous system (brain and spinal cord).
– Endocrinologist – to treat hormone imbalances in the case of McCune-Albright syndrome.