Fibrous dysplasia: Difference between revisions

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= Diagnosis =
= Diagnosis =
[[File:Fibrous dysplasia.png|thumb]]
* CT Imaging: Expansile remodeling of bone, ground-glass appearance.
* CT Imaging: Expansile remodeling of bone, ground-glass appearance.
* MRI: For cranial nerve compression.
* MRI: For cranial nerve compression.
* Histology: “Chinese figure” formation in bone trabeculae.
* Histology: “Chinese figure” formation in bone trabeculae.
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= Treatment =
= Treatment =

Latest revision as of 21:46, 2 March 2024

Introduction

  • A benign fibro-osseous lesion of immature mesenchymal cells.
  • Commonly affects long bones, ribs, and skull.

Pathophysiology

  • Originates from mutated pluripotent embryonic cells leading to skeletal stem cells.
  • Lesions form as cancellous bone is replaced with fibrous tissue and immature woven bone.
  • Monostotic FD (70% of cases) vs. Polyostotic FD.

Genetic Basis and Related Syndromes

  • Genetic mutation: Chromosome 20q13 at the GNAS1 locus.
  • Constitutively active mutant of the α subunit of the G protein (Gsα).
  • McCune-Albright syndrome: Characterized by polyostotic FD, endocrinopathy, café au lait spots.


Clinical Presentation

  • Monostotic FD usually presents by age 30.
  • Polyostotic FD presents in early childhood.
  • Symptoms: Painless osseous expansion, facial asymmetry.
  • Craniofacial involvement: Ethmoid (71%), Sphenoid (43%), Frontal (33%), etc.


Diagnosis

  • CT Imaging: Expansile remodeling of bone, ground-glass appearance.
  • MRI: For cranial nerve compression.
  • Histology: “Chinese figure” formation in bone trabeculae.


Treatment

  • Asymptomatic lesions: Conservative management.
  • Medications: Alendronate (bone density), Denosumab (reduces pain but concerns over side effects).
  • Surgical options: Contouring, total resection, computer-based planning, timing for children.

Considerations

  • McCune-Albright syndrome management.
  • Orbital apex involvement: Proptosis, diplopia, and options for optic nerve compression.
  • Malignant transformation: Rare (0.4 to 4%).