Fibrous Dysplasia


Fibrous dysplasia is an uncommon condition in which fibrous bone forms within normal bone. Fibrous dysplasia is not cancer but the areas of the bone where the fibrous tissue forms have a tumor-like appearance, so fibrous dysplasia is often described as a benign bone tumor.

The condition is usually diagnosed in childhood, but it is a ‘chronic’ condition so it continues into adulthood and may be diagnosed in adulthood. Fibrous dysplasia can affect more than one bone with the most common sites being in the long bones of the arms and legs, as well as the pelvis, ribs and skull.

As mentioned, fibrous dysplasia is not cancer but as with other benign bone tumors there is a very slight (less than 1%) chance it will become cancerous.1 Therefore, once diagnosed, it is important to have regular follow-up visits with an orthopedic surgeon with expertise in bone tumors to assure the condition doesn’t transform to a cancerous process.

Causes of Fibrous Dysplasia

Fibrous Dysplasia is caused by a gene mutation. This mutation “tells” cells to produce fibrous tissue instead of bone. It is not a hereditary condition so it is not passed to children from their parents but it can be associated with other syndromes such as McCune-Albright syndrome and neurofibromatosis II.1

Signs and Symptoms of Fibrous

Dysplasia Fibrous dysplasia can cause pain in the bone where the abnormal tissue is growing; this growth causes the bone to expand which gives the appearance of swelling in the area. The abnormal growth and expansion may result in deformities of the affected bones. Because the fibrous areas are weaker than normal bone, there is a risk of the bone breaking (fracture) at the area of abnormal bone. This can also be a source of pain. Pain and bone deformity often have an impact on how someone functions. There may be a reluctance to use the affected extremity or a noticeable limp if the leg is affected. Fibrous dysplasia can affect the glands that produce hormones.

Symptoms that may develop in this situation include:

  • Early puberty 
  • Anxiety and weight loss (if the thyroid is affected)
  • Weight gain (if the adrenals are affected)
  • High blood calcium levels (if the parathyroids are affected)
  • Pigmented skin lesions (‘café-au-laut’ spots)

Diagnosing Fibrous Dysplasia

An x-ray is usually the first test when a person describes symptoms of extremity pain or deformity. On an x-ray, the abnormal fibrous areas look like ground glass and the bone may appear to be expanding. The x-ray may also show a bowing deformity of the affected bone. One of the most obvious signs when fibrous dysplasia affects the upper thigh bone (near the hip) is a shepherd’s crook deformity where the bone is bowed in the shape of a shepherd’s crook (cane).

A CT (CAT) scan may be obtained if the area has fractured. This will better show the extent of the fracture and aid in the decision of management of the fracture. It can also help in assessing the amount bone deformity.

A bone scan can detect other areas of the skeleton that might be affected by this condition.

If the x-ray shows areas of bone destruction in addition to the ground glass appearance there may be concern that the area has become cancerous. If this is the case, other tests will be requested to assess for this possibility.

These include:

  • Biopsy – to analyze the cells and determine if there is a cancerous process
  • MRI – if a cancerous process is confirmed an MRI is used to determine if it has spread to the surrounding soft tissues as well as other areas of the body

Treatment of Fibrous Dysplasia

There is no cure for fibrous dysplasia; rather, it is a condition that is often managed by the symptoms a person is experiencing. If there are no symptoms then periodic x-rays to monitor the abnormal bone may be all that’s recommended.

  Medications
Osteoporosis medications that help strengthen bones may be used for fibrous dysplasia. In addition to strengthening the bone, they can have some affect in helping to relieve the pain associated with the condition.2  Pain medications may be prescribed if the pain is not responding to over-the-counter medications. These are usually for short-term management of periods of increased pain.
  Surgery
Surgery is often recommended if the bone has fractured or if a more conservative approach like bracing or casting won’t be effective. Surgery may be considered to correct a deformity that is significantly affecting someone’s function. Regular follow-up is often recommended to assure no cancerous process is occurring. Management by a specialist with knowledge of extremity tumors is best as they have expertise in recognizing abnormal changes in benign bone or soft tissue lesions.

Regular follow-up is often recommended to assure no cancerous process is occurring.

Management by a specialist with knowledge of extremity tumors is best as they have expertise in recognizing abnormal changes in benign bone or soft tissue lesions.


References
1. Leet AI, Collins MT; Current approach to fibrous dysplasia of bone and McCune-Albright syndrome; J Child Orthop. 2007 Mar; 1(1): 3–17
2. Chapurlat R, Delmas PD, Liens D, Meunier PJ Long-term effects of intravenous pamidronate in fibrous dysplasia of bone. J Bone Miner Res (2002) 10:1746–1752
3. National Institutes of Health Osteoporosis and Related Bone Diseases ~ National Resource Center; January 2012