Fibrous dysplasia of bone

A benign developmental condition – replacement of normal medullary bone with abnormal fibrous CT proliferation with the capacity to form new metaplastic bone

Clinical: 3 main presentations, all of which involve the skull and jaws

  1. Monostotic disease – Painless swelling
  2. Polyostotic non syndromic disease.
  3. Polyostotic syndromic type:
    • Jaffe type:
      – Polyostotic FD
      – Cutaneous pigmentation (café au lait spots)
    • McCune Albright syndrome:
      – Polyostotic FD
      – Cutaneous pigmentation (cafe au lait spots)
      – Endocrine hyperfunction – precocious puberty, acromegaly, hyperthyroidism, hyperparathyroidism, hyperprolactinaemia
  • Asymptomatic, self limiting, stabilizing at puberty and growing slowly thereafter


  • Gs alpha mutation (chromosome 20) – which transcribes transmembrane signaling proteins.
  • Resultant dysfunction in cAMP signaling affects multiple systems.
  • In the musculoskeletal system:
    – Osteoblasts secrete abnormal bone
    – ↑ IL-6 – ↑ Osteoclastic bone remodeling
  • The severity of the condition depends of the timing of the mutation and the size of the affected cell mass:
    • a) Mutations in embryonic life -Polyostotic and syndromic types (20 %).
    • b) Postnatal mutations – Monostotic types (80 %)

Common site: Maxilla > mandible, with jaws being the most common site but ribs, femur and tibia are also commonly affected


  • Early lesions – Radiolucent, with a unilateral “ground glass” appearance being acquired in the process of calcification.
  • Ill defined margins
  • Bucco-lingual expansion pattern
  • Loss of lamina dura around root
  • No displacement of teeth and no resorption

Lab: Serum laboratory values are normal


  • Irregularly shaped trabeculae – of immature woven bone – in cellular, loosely arranged
    fibrous stroma.
  • Metaplastic deposits of curvilinear bone arranged in ”chinese letter” pattern
  • Few osteoblasts, no osteoclasts and no inflammatory cells – except 2⁰ infection


  • Surgical recontouring/bone shaving
  • Alleviate pain, pressure and deformity
  • Bisphosphonates
  • May recur (25%)


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