Fibrous dysplasia of bone

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Fibrous dysplasia
Micrograph showing fibrous dysplasia with the characteristic thin, irregular (Chinese character-like) bony trabeculae and fibrotic marrow space. H&E stain.
Classification and external resources
Specialty medical genetics
ICD-10 K10.8, M85.0, Q78.1

526.89, 733.29,

MedlinePlus 001234
eMedicine radio/284
MeSH D005357

Fibrous dysplasia is an abnormal bone growth where normal bone is replaced with fibrous bone tissue. It causes abnormal growth or swelling of bone. It 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 vara 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.[1][2] It is not hereditary.[3] There are three types of fibrous dysplasia:

  1. Monostotic (Involving a single bone, or adjacent bones, like both the upper and lower jaw)
  2. Polyostotic (Involving many bones).
  3. Panostotic (Involving every bone).[4]

The most severe form of polyostotic fibrous dysplasia is known as McCune-Albright syndrome. Fibrous dysplasia of bone may also be an associated abnormality in Neurofibromatosis type II.


Fibrous dysplasia of the right zygomatic bone (left in the image). Corresponding T2-weighted MRI (left) and CT (right) of the same patient.

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.

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)
Micrograph of fibrous dysplasia (right of image) jutxaposed with unaffected bone (left of image). H&E stain


Treatment options may include:

  • Medication to strengthen bones (amino-bisphosphonates)
  • Medication to treat onset of pain
  • Pain management therapy
  • Surgery

See also


External links