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Fibrous dysplasia (FD) is a rare condition where normal bone is replaced by softer, weaker fibrous tissue. This can make bones more likely to ache, bend, or break. FD is not something a person inherits, and it is not cancer. In very rare cases, though, a lesion can become cancerous. FD is part of a group of related conditions known as fibrous dysplasia/McCune-Albright syndrome (FD/MAS), caused by a change in a gene called GNAS.
Because FD can look different in each person – sometimes affecting just one bone, sometimes many – it can be confusing and overwhelming after a diagnosis. This page breaks down what causes it, what symptoms to expect, how doctors diagnose it, and what treatment and daily life with FD can look like.
What Causes Fibrous Dysplasia?
FD happens because of a random change in a gene called GNAS early in development. This change isn’t inherited. It happens after conception, so only some of the body’s cells are affected. Scientists call this mosaicism.1
This gene change makes some bone-forming cells work incorrectly. Instead of creating strong, organized bone, they make a softer mix of fibrous tissue and immature bone. That weaker structure can cause pain, bowing, or fractures over time.2
The earlier the mutation happens during development, the more widespread the disease might be. Some people have only one bone affected, while others have several. In rare cases, other body systems, like hormone glands or skin, can also be involved, which means the person is described as having Fibrous Dysplasia/McCune-Albright Syndrome (FD/MAS).3
Types of Fibrous Dysplasia
Doctors usually describe FD in two ways:
- Monostotic FD means only one bone is affected. This is the most common form.
- Polyostotic FD means multiple bones are affected. This form tends to appear earlier in life and can cause more symptoms.4
Polyostotic FD is more likely to cause problems with bone shape, and movement, it may also cause pain. FD can also occur with McCune-Albright syndrome, which adds hormone changes and areas of light-brown birthmarks sometimes called café-au-lait spots.
Common Symptoms
The signs and symptoms of FD depend on which bones are affected and how severe the disease is.
General Symptoms
- Bone pain: a common complaint, sometimes constant, sometimes worse with activity.
- Fractures: Weakened bones can break more easily, especially in the legs, ribs, and arms.
- Changes in bone shape: Bones can curve or become uneven and deformed, causing a limp or uneven shoulders or hips.
If the Skull or Face Is Affected
- Changes in facial shape or asymmetry
- Bulging eyes (proptosis)
- Problems with hearing or vision if bone thickens near nerves.5
Dental Changes
When FD affects the jaw, it can shift teeth or cause weak enamel and cavities.
How the Condition Changes Over Time
Lesions often grow while a person is still growing and may slow or stop once growth ends. For some people, though, changes continue into adulthood. Bone changes are often linked to hormonal changes.
How Do Doctors Diagnose FD?
Fibrous dysplasia of the right zygomatic bone (left). Corresponding T2-weighted MRI (left) and CT (right) of the same patient. Credit: Wikipedia
Doctors use a mix of medical history, physical exams, and imaging tests to diagnose FD. Sometimes a small sample (biopsy) or genetic test is needed to confirm it.
Imaging Tests
- X-rays are often the first test. FD shows up as cloudy or “ground-glass” areas where the bone looks different from normal bone.
- CT or MRI scans provide detailed pictures and help doctors see whether the affected bone is pressing on nerves, sinuses, or nearby structures.6
- Bone scans can show how many bones are affected. They’re sometimes used to get a full picture of the disease.
Genetic or Biopsy Tests
Blood or saliva tests rarely find the FD mutation because only some cells carry it. If imaging isn’t clear, a doctor may recommend a bone biopsy to confirm the diagnosis.7
Ruling Out Other Conditions
Other bone conditions, like ossifying fibroma, can look similar. A biopsy or second opinion from a bone specialist can help confirm FD.
Treatment and Management
There isn’t a cure for FD yet, but treatment can manage symptoms and help prevent complications. Care is usually provided by a team that may include orthopedic surgeons, endocrinologists, dentists, and pain specialists. Reviewing the full treatment guidelines with your care team is strongly recommended.
Medications
- Pain management: Over-the-counter medicines like ibuprofen or acetaminophen often help. For ongoing pain, doctors may recommend stronger medications or a referral to a pain clinic.
- Bisphosphonates: These drugs can reduce bone turnover and may help with pain, though they don’t stop lesions from forming.8
- Denosumab: A newer medication being studied for FD. It may help control pain or slow bone changes but is not yet standard treatment.
- Vitamin D and calcium: Work with a care team to manage levels and review supplements. These are important for keeping bones strong and reducing fracture risk.
Surgery
Surgery may be needed if FD causes repeated fractures, significant deformity, or pressure on nerves. Surgeons can straighten or stabilize bones using rods, plates, or grafts. Craniofacial surgery can improve vision, relieve nerve pressure, or correct bone shape, though regrowth can occur. Watchful waiting is often recommended, as surgery can be a significant burden.
Ongoing Care
- Children and teens need close monitoring since lesions may grow with them.
- Adults may only need periodic checkups if their disease is stable.
- Regular eye, ear, and dental exams are important if FD affects the skull or face.
Outlook
Many people with FD live normal, active lives. Those with only one affected bone often have few long-term problems. When multiple bones are involved, it can be more complicated, but good care helps most people stay mobile and independent.
- Lesions may stop changing once growth is complete.
- Cancer in FD is extremely rare (less than 1%), but radiation to the affected bone can raise that risk.9
- Researchers are studying treatments that target the genetic pathway behind FD, offering hope for more direct therapies in the future.
Living With Fibrous Dysplasia
A diagnosis of FD can feel isolating. Pain, fatigue, or visible bone changes can affect self-esteem, work, and daily life. Emotional support is as important as medical care.
Organizations like the FD/MAS Alliance offer patient stories, research updates, and a community of people who understand what you’re going through. Connecting with others can make a big difference.
Key Takeaways
Fibrous dysplasia is a rare bone condition that affects everyone differently. It is not inherited or contagious, and most people live full lives with proper care. While there’s no cure yet, treatments and community support can greatly improve quality of life.
Related Pages:
- What are the symptoms of Fibrous Dysplasia?
- Treatment options for Fibrous Dysplasia
- Tests commonly performed in FD/MAS
- FD/MAS Toolkit
Frequently Asked Questions
Is fibrous dysplasia inherited?
No. FD happens by chance and isn’t passed from parents to children. It results from a random change in the GNAS gene that occurs after conception, meaning it affects only some of the body’s cells. Families don’t need to worry about passing it on to their children.
Can fibrous dysplasia become cancer?
It’s very rare, less than one in a hundred cases. The risk can increase if the affected bone has been exposed to radiation. Most people with FD will never experience this complication. Regular monitoring helps doctors catch any unusual changes early.
Do bisphosphonates cure FD?
No. These medications don’t remove or reverse FD lesions, but they can help reduce bone pain and lower bone turnover. Many patients find that bisphosphonates make their day-to-day discomfort more manageable, but the effect varies from person to person.
Does FD stop progressing after puberty?
Often it does. For many people, lesions slow down or stop growing once they reach skeletal maturity. However, some adults continue to experience slow changes or new symptoms over time, so continued checkups and imaging remain important into adulthood even after growth stops.
Can I exercise or play sports if I have FD?
In most cases, yes, but it depends on which bones are affected and how severe the disease is. Low-impact activities like swimming, cycling, or walking are often recommended. High-impact or contact sports may increase the risk of fractures, so it’s best to discuss safe options with your doctor or physical therapist.
Can FD spread to other parts of the body over time?
FD doesn’t spread like an infection or cancer. However, existing lesions can grow or change, especially during childhood and adolescence. Regular checkups and imaging can help track any changes and manage symptoms early.
References
- Endocrine Reviews, 2020 – Fibrous Dysplasia Overview
- Medscape – Fibrous Dysplasia of Bone
- NCBI Bookshelf – Fibrous Dysplasia/McCune-Albright Syndrome
- PMC, 2024 – Clinical Spectrum of FD
- Orphanet Journal of Rare Diseases, 2012 – Craniofacial FD
- Insights Imaging, 2018 – Imaging of FD
- PMC, 2024 – Diagnosis and Genetics of FD
- PMC, 2016 – Bisphosphonate Therapy for FD
- NCBI Bookshelf – Cancer Risk in FD