Fibrous dysplasia of bone
|Classification and external resources|
|ICD-10||K10.8, M85.0, Q78.1|
Fibrous dysplasia is an abnormal bone growth where normal bone is replaced with fibrous bone tissue. Fibrous dysplasia causes abnormal growth or swelling of bone. Fibrous dysplasia can occur in any part of the skeleton but the bones of the skull, thigh, shin, ribs, upper arm and pelvis are most commonly affected. Fibrous dysplasia is very rare, and there is no known cure. Fibrous dysplasia is not a form of cancer.
Most lesions are monostotic, asymptomatic and identified incidentally and can be treated with clinical observation and patient education.
This disorder is usually diagnosed in childhood or early adulthood and can affect one or several bones. Males and females of any race are equally affected.
In fibrous dysplasia, the medullary cavity of bones is filled with fibrous tissue, causing the expansion of the areas of bone involved. The bony trabeculae are abnormally thin and irregular, and often likened to Chinese characters (bony spicules on biopsy). Fibrous dysplasia is characterized by Shepherd Crook's deformity which refers to a coxa varus angulation of the proximal femur.
The cause of this transformation, in turn, is not completely known, however. Levels of the transcription factor C-fos are raised in fibrous dysplasia, leading to gene over-expression and tumour formation. It is not hereditary. There are two types of fibrous dysplasia:
- Monostotic (Involving a single bone, or adjacent bones, like both the upper and lower jaw)
- Polyostotic (Involving many bones).
Especially when involving the skull or facial bones, the lesions can cause externally visible deformities. The skull is often, but not necessarily, affected, and any other bone(s) can be involved.
- Many patients have lesions localized in only one bone (monostotic fibrous dysplasia), affecting 70–80%.
- Others have them in many bones (polyostotic fibrous dysplasia).
In 3% of cases, people suffering from fibrous dysplasia also have endocrine diseases and skin pigmentation; the three together constitute McCune-Albright syndrome. These endocrine diseases include precocious (early) puberty, often occurring as early as 3 years old.
In most cases, fibrous dysplasia has no symptoms and is only diagnosed by accident during investigations for an unrelated medical problem. When symptoms occur, they can include:
- Pain - caused by the expansion of bone. Treatment for this is pain management therapy, analgesics and anti-inflammatory medication.
- Irregular bone growth
- Bone deformity
- Increased susceptibility to bone fractures (rare)
Treatment options may include:
- Medication to strengthen bones (amino-bisphosphonates)
- Medication to treat onset of pain
- Pain management therapy
- Candeliere GA, Glorieux FH, Prud'homme J, St-Arnaud R (June 1995). "Increased expression of the c-fos proto-oncogene in bone from patients with fibrous dysplasia". N. Engl. J. Med. 332 (23): 1546–51. doi:10.1056/NEJM199506083322304. PMID 7739708.
- Kashima TG, Nishiyama T, Shimazu K, et al. (February 2009). "Periostin, a novel marker of intramembranous ossification, is expressed in fibrous dysplasia and in c-Fos-overexpressing bone lesions". Hum. Pathol. 40 (2): 226–37. doi:10.1016/j.humpath.2008.07.008. PMID 18799196.
- Fibrous Dysplasia at eMedicine
- MRI showing fibrous dysplasia of the femoral neck
- Duke Orthopedics fibrous_dysplasia
- Fibrous Dysplasia Pictures MedPix Imaging Database
- Fibrous Dysplasia of the Skull Images radRounds Radiology Image Database
- Fibrous dysplasia from Radiopaedia.
- Fibrous Dysplasia Foundation