Fibrous Dysplasia is a rare and chronic bone disorder caused by a gene mutation in bone-producing cells, osteoblasts. The cells then produce abnormal fibrous bone. Most often fibrous dysplasia affects the skull, legs, arms, ribs, and pelvis. Once weakened these bones are prone to pain, fracture and bowing.  When this condition affects the bones in the skull, they can expand, causing pain and visible malformations.

Approximately 70-80 percent of patients experience the monostotic form of the disease, which affects only one bone and may be asymptomatic.  Polyostotic fibrous dysplasia occurs in multiple bones, is generally more aggressive, and can on rare occasions become malignant.  Existing lesions may grow, but new lesions rarely develop after age 15.  

In about three percent of patients, the skin and endocrine system also are affected, indicating a disorder known as McCune-Albright Syndrome.  Café-au-lait spots (benign pigmented skin lesions), early-onset puberty, and hormonal imbalances also can develop.   
There is no known cause or cure for fibrous dysplasia.  Medications are used to relieve the pain and surgery may be needed to treat the affected bones.  

Patient with fibrous dysplasia since childhood and an area that converted into an aggressive osteosarcoma


The cause of fibrous dysplasia is unknown and no genetic or environmental factors have been identified.

Risk Factors

Risk factors associated with an increased chance of developing fibrous dysplasia are unknown.  


  • Pain (more likely on weight bearing leg and pelvis)
  • Limp
  • Fracture
  • Mass
  • Deformity of facial bones (can cause loss of vision or hearing)
  • Deformity of long bones (can cause arthritis in joints)
  • Café-au-lait spots
  • Low blood phosphorous

If hormonal abnormalities occur patients may present with:

  • Early-onset puberty (most often in girls)
  • Anxiety
  • Weight loss or gain
  • Abnormal sweating
  • Diabetes
  • Milk production in women
  • Gigantism/Acromegaly
  • Elevated blood calcium


A diagnosis of fibrous dysplasia is confirmed by:  

  • X-Ray
  • CT
  • MRI
  • Bone Scans
  • Blood Tests
  • Urine Tests

Coronal view of the same patient showing both area of bony overgrowth & osteosarcoma


Treatment includes pain management and fracture prevention. Surgery is indicated when lesions or fractures are causing intolerable symptoms that don’t respond to non-surgical interventions, when bones fracture into separate pieces, if cancer is present, or to remove a progressive deformity.

  • Medication (bisphosphonates for pain relief)
  • Braces (to prevent fractures)
  • Surgical resection with bone graft
  • Reconstruction with cortical bone allographs
  • Fixation with an intramedullary rod
  • Osteotomy

Surgical treatment of craniofacial fibrous dysplasia:

Craniofacial fibrous dysplasia can be functionally and cosmetically disruptive.  The surgical treatment involves shaving the bone or removing it and reconstructing it.  The neurosurgeon will consider the location and how aggressive the lesion is, as well as the general health and preferences of the patient.  The surgical team may include an otolaryngologist and/or an ophthalmologist, as visual impairment due to compression of the optic nerve is common.  Reconstruction is done immediately by grafting another bone onto the affected area. As minimally invasive, transnasal approaches have evolved fibrous dysplasia of the skull base can now be removed through the nose.


There is no known way to prevent fibrous dysplasia.

If you want to learn more about treatment for fibrous dysplasia, call the Mount Sinai Department of Neurosurgery at 212-241-2377.
Images used with permission from Joshua B. Bederson, MD


Last updated June 8, 2011