What is Fibrous Dysplasia?
Fibrous dysplasia is a generally non-cancerous condition where abnormal growth, or proliferation, of fibro-osseous (containing both fibrous tissue and bone) occurs within the bone marrow due to altered bone formation. This was first defined by Lichtenstein and Jaffe in 1942 and was originally called Jaffe-Lichtenstein syndrome. It can happen in one bone (monostotic) or multiple bones (polyostotic).
When fibro-osseous tissue replaces normal bone, complications can arise. These may include fractures or pressure on nearby soft tissues like nerves and blood vessels. The monostotic form often doesn’t cause any symptoms while the polyostotic form generally shows up during childhood. Adult cases are usually accidentally found during imaging tests done for unrelated reasons.
The abnormal bone can lead to fractures, especially in bones that bear weight or in the upper limbs of athletes. Although uncommon, it can occasionally turn cancerous, particularly following radiation therapy. McCune-Albright syndrome is a relatively uncommon condition that consists of fibrous dysplasia in multiple bones commonly on one side, skin pigment abnormalities, and hormonal issues (often early puberty in girls). Mazabraud syndrome is a very rare version of the polyostotic form that occurs with single or multiple myxomas (benign tumors) within the muscles.
What Causes Fibrous Dysplasia?
Fibrous dysplasia, a bone disorder, has been connected to a particular type of mutation in the GNAS1 gene on chromosome 20. This mutation causes fibrous tissue, a kind of connective tissue in the body, to grow excessively.
Risk Factors and Frequency for Fibrous Dysplasia
Fibrous dysplasia is usually detected in children or young adults, and it doesn’t lean towards any gender. This diagnosis estimates to occur in 1 of every 5,000 to 10,000 individuals. It accounts for 5% of all benign, or non-cancerous, bone issues. There are different types of fibrous dysplasia, and the most common is the monostotic form, which represents 75% to 80% of all fibrous dysplasia cases.
Signs and Symptoms of Fibrous Dysplasia
Monostotic fibrous dysplasia is a condition where bones develop abnormally, often with no symptoms. Some people might experience bone pain or fractures even with minor injuries. This condition can become more noticeable during pregnancy, leading to increased bone pain and the risk of fractures. Mild symptoms or none at all are typically observed when the disease only affects the bones. When evaluating for this disease, doctors may ask about bone tenderness, unusual bone growths, uneven bone structure, hormone issues, and skin complaints. This disease can run in families in some cases, like with a condition called cherubism. In rare cases, less than 1% of people with this condition could develop cancer. Regular check-ups are important for identifying aggressive growths in patients with fibrous dysplasia. McCune-Albright syndrome, a condition involving hormone issues, might be considered in certain cases.
Physical examinations may only play a minor role in identifying fibrous dysplasia lesions. In cases of fracture-induced pain, pressing on the area may increase discomfort. Observing for abnormalities in bone structure can help indicate the presence of the disease. Differences in leg length could indicate a condition creating an abnormal curvature of the thigh bone, known as a shepherd’s crook deformity. Changes to the face, including asymmetry, swollen eye areas, broad forehead, or an enlarged lower jaw, can also be signs.
Common areas affected by this condition include the ribs, long bones, and facial structures. Less commonly, the hands, sternum, and spine are affected. In patients with McCune-Albright syndrome, doctors may also examine the skin for light brown spots. Skin acne might indicate a hormonal issue, like Cushing syndrome. A comprehensive examination of the endocrine system is important. This includes evaluating the heart and lungs, digestive system, and thyroid. If the fibrous dysplasia affects facial structures, vision and hearing tests might also be important.
Testing for Fibrous Dysplasia
Imaging is used as a key tool in diagnosing the condition and figuring out how far the disease has spread. First, a common X-ray is used. More advanced imaging tools, such as computerized tomography (CT) and magnetic resonance imaging (MRI), might be necessary to rule out other problems in your bones. These tools can also assess damage from fractures, complications in the brain’s blood vessels and nerves, and check for rare transformations into dangerous diseases. CT and MRI can also be useful to check for issues with adrenal glands, thyroid nodules, and pituitary gland tumors.
Typically, bone lesions will appear as an internal ground glass matrix on X-rays and CT images. However, they can also look different, for instance, they might look like they’re dissolving (lytic) or hardening (sclerotic). They might also cause bones to expand or the bone’s outer layer to become thinner.
Imaging can also bring to light issues such as bone bending (including a deformity known as the femoral shepherd’s crook), discrepant limb length, and short stature due to premature closure of growth plates. A bone scan that indicates high uptake of Technetium-99m may be used to see how extensively the disease has spread in cases where many bones are affected. Lastly, if the features of the imaging mimic conditions that are malignant (cancerous), a biopsy (a procedure where tissue is removed and examined) might be needed.
Treatment Options for Fibrous Dysplasia
Monostotic fibrous dysplasia, a condition where one bone develops abnormally, often doesn’t cause any symptoms. In these cases, patients are regularly checked for any new signs of the condition with the help of X-ray images. If you don’t experience any issues, you generally don’t need treatment.
However, if you do have symptoms like bone pain or osteoporosis (a condition where bones become weak and brittle), your doctor might recommend a type of medication known as bisphosphonates. These medications can help lessen your bone pain and strengthen your bones, reducing the chances they’ll break.
Surgery can be considered if the fibrous dysplasia is causing problems. For example, if the condition has caused a bone to break or if it’s made the bone weak enough that it’s likely to break, your doctor might recommend a procedure to reinforce the bone. There may also be additional surgical interventions for correcting deformities in the limbs and spine, or discrepancies in limb length.
If you’re experiencing issues like nerve compression symptoms due to fibrous dysplasia in your face and skull, craniofacial surgery may help. This type of surgery can include removing the affected parts of the bone, grafting in healthy bone, and inserting hardware like metallic rods, plates, and screws to secure the area.
What else can Fibrous Dysplasia be?
When it comes to identifying McCune-Albright syndrome, a condition that affects many bones in the body, it’s important to pay careful attention to the unusual skin marks, or café au lait spots, that accompany it. These spots often have jagged edges, unlike the smooth borders seen in skin marks associated with a different condition called neurofibromatosis.
Figuring out if someone has a condition called fibrous dysplasia, which is often seen in people with McCune-Albright syndrome, can be difficult. There are many other bone conditions that can appear similar on medical images. In cases where only one bone is affected, the condition can seem like:
- A simple bone cyst
- A giant cell tumor
- Fibroxanthoma
- Osteoblastoma
- Hemangioma
- Osteofibrous dysplasia
- Paget disease
When many bones are affected, it can also look like other diseases such as:
- Neurofibromatosis
- Hyperparathyroidism
- Enchondromatosis
- Eosinophilic granuloma
However, there are certain hints doctors can look out for that may suggest fibrous dysplasia. These include the patient’s age, which bones are affected (fibrous dysplasia usually affects the long bones), the presence of a specific pattern on the bone called a ground glass matrix, and the lack of aggressive features typically seen in cancerous bone tumors. When these factors aren’t enough to rule out cancer, a bone biopsy may be needed.
Possible Complications When Diagnosed with Fibrous Dysplasia
Fibrous dysplasia often affects only one bone and doesn’t show symptoms. However, severe bone changes can cause harm. Bone curvature may interfere with normal muscle and joint function or speed up the development of arthritis. Abnormalities in the spine can lead to scoliosis and related impacts on daily activities.
This disease can also affect the skull and facial bones, potentially causing loss of vision and hearing due to nerve damage. A very rare complication is the development of a certain type of cancer, known as sarcoma. This complication is especially possible if the patient has had radiation therapy in the past.
Common Examples:
- Monostotic fibrous dysplasia (affects only one bone)
- Severe bone changes causing muscle and joint problems
- Development of arthritis
- Scoliosis due to spine abnormalities
- Functional limitations from scoliosis
- Cranial nerve damage causing loss of vision and hearing
- Rare transformation to sarcoma, especially after radiation therapy
Preventing Fibrous Dysplasia
It’s crucial for patients to understand the potential risk for bone fractures, especially in cases of craniofacial diseases – conditions affecting the head and face. These patients need to be aware of and look out for any developing issues with their nerves that could lead to loss of vision or hearing.
In the case of McCune-Albright syndrome, this is a condition that can affect many parts of the body. It’s important that both the patient and their parents are well-informed about the different ways the syndrome can present itself. Genetic counseling, which is a service that provides information and support to people who have, or may be at risk for, genetic disorders, should also be included.
Furthermore, patients should have regular check-ups with an endocrinologist- a doctor specialized in hormones. This is to keep an eye out for any symptoms of endocrine dysfunction, a condition that occurs when your hormone levels are out of balance.