Updated: 10/22/2017

Fibrous Dysplasia

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Questions
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Cases
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Introduction
  • A developmental abnormality caused by failure of the production of normal lamellar bone
    • areas of the skeleton remain poorly mineralized trabeculae
  • Epidemiology
    • demographics
      • male:female ratio
        • females > males
      • age bracket
        • found in any and all ages
        • onset for 75% of patients at <30 years of age
    • location
      • any bone can be involved
      • the proximal femur is most common site, followed by rib, maxilla, and tibia
  • Genetics
    • GS alpha protein (chromosome 20q13) activating mutation (affects cAMP signaling pathway leading to increased production of cAMP)  
    • not inherited
    • high production of FGF-23 which may lead to hypophosphatemia
  • Associated conditions
    •  orthopedic manifestations
      •  McCune Albright syndrome  
        • condition defined by the presence of
          • skin abnormalities (cafe au lait spots in coast of Maine pattern)
          • endocrine abnormalities (precocious puberty)\
            • renal phosphate wasting due to FGF-23 (oncogenic osteomalacia)
          • unilateral polyostotic fibrous dysplasia
            • obtain AP spine radiographs to look for scoliosis
      • Mazabraud syndrome
        • polyostotic fibrous dysplasia
        • soft-tissue intramuscular myxomas
      • Osteofibrous dysplasia
        • rare form that primarily affects the tibia and is confined to the cortices
    • nonorthopedic manifestations
      • severe cranial deformities with blindness
  • Prognosis
    • 1% risk of malignant transformation to osteosarcoma, fibrosarcoma, or malignant fibrous histiocytoma
      • poor prognosis
Presentation
  • Symptoms
    • usually asymptomatic and discovered as an incidental finding
    • may have swelling or deformity
    • bone lesions may be monostotic (80%) or polystotic (20%)
    • pain from stress fractures
  • Physical exam
    • inspection
      •  cafe au lait spots
        • larger and more irregular borders than neurofibromatosis
        • may or may not be present with fibrous dysplasia
        • by definition present with McCune-Albright syndrome
      • swelling around lesion
Imaging
  • Radiographs
    • hip/pelvis radiograph
      • central lytic lesions in medullary canal (diaphysis or metaphysis)
      • may have cortical thinning with expansile lesion
      • highly lytic lesions or a ground glass appearance
      • "punched-out" lesion with well defined margin of sclerotic bone is common 
      • modest expansion of bone
      • Shepherd's crook deformity
    • AP spine radiograph 
    •  
      • vertebral collapse 
      • kyphoscoliosis
  • Bone scan
    • usually warm
Studies
  • Gross - yellow-white gritty tissue
  • Histology
    • characteristic look of "alphabet soup" or "chinese letters"
    • fibroblast proliferation surrounding islands of woven bone
      • woven bone lacks osteoblastic rimming (osteofibrous dysplasia has osteoblastic rimming)
    • trabeculae of osteoid and bone in fibrous stroma with metaplastic cartilage or areas of cyst degeneration
    • mitotic figures are common
Treatment
  • Nonoperative
    • observation
      • indications
        • asymptomatic patients
    • Bisphosphonate therapy
      • indications
        • symptomatic polyostotic fibrous dysplasia
      • effective in decreasing pain and reducing bone turnover
  • Operative
    • internal fixation and bone grafting
      • indications
        • symptomatic lesions
        • impending/actual fractures through lesions in areas of high stress (femoral neck)
        • severe deformity
        • neurologic compromise in the spine
      • technique
        • never use autogenous cancellous bone, as the transplanted bone will quickly turn into fibrous dysplastic woven bone
        • use cortical or cancellous allografts
        • intramedullary device more effective than a plate in the lower extremity
    • osteotomies
      • indications
        • coxa vara deformity
          • intertrochanteric osteotomy 
Differentials & Groups
 
Multiple lesions in young patients (1)
 
Treatment is Observation alone (2)
 
Benefits from Bisphonate therapy
   
Fibrous dysplasia
 
 
   
Eosinophilic granuloma
 
 
 
   
Lymphoma
     
 
   
Leukemia
     
 
   
Enchondroma / Olliers / Marfucci's
 
 
 
   
Osteochondroma / MHE
 
 
 
   
NOF / Jaffe-Campanacci syndrome
 
 
 
   
Hemangioendothelioma
     
 
   
Paget's
 
 
 
   
Metastatic Disease        
   
Myeloma
 
 
 
 
   
ASSUMPTIONS: (1) Younger patient is < 40 yrs; (2) assuming aymptomatic and no impending fracture
 
IBank
 
Location
Age
Xray
Xray
CT
B. Scan
MRI
MRI
Histo(1)
Case A fibula
10 yrs.
   
   
Case A spine  
 
 
Case B radius  
 
     
Case C humerus  
 
 
   
Case D skull  
 
       
(1) - histology does not always correspond to clinical case

 

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Questions (16)
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(OBQ06.240) A genetic abnormality in the cyclic AMP signaling pathway is involved in which of the following conditions? Review Topic

QID: 251
1

Achondroplasia

11%

(80/705)

2

Hypochondroplasia

4%

(29/705)

3

Multiple hereditary exostosis

13%

(90/705)

4

Fibrous dysplasia

63%

(446/705)

5

Neurofibromatosis type I

8%

(57/705)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(OBQ07.231) A 17-year-old high-school track athlete complains of vague pain along his knee. He denies any specific trauma to this area. A radiograph is seen in Figure A. A biopsy specimen in low and high power is seen in Figure C and D, respectively. What is the most likely diagnosis? Review Topic

QID: 892
FIGURES:
1

Adamantinoma

26%

(515/1995)

2

Osteomyelitis

0%

(9/1995)

3

Fibrous dysplasia

63%

(1255/1995)

4

Osteosarcoma

5%

(104/1995)

5

Stress fracture

5%

(102/1995)

ML 3

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PREFERRED RESPONSE 3
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(SBQ13PE.1) A 6-year-old being evaluated in your clinic presents with the clinical findings and radiographs shown in Figures A and B. What is the most likely diagnosis?
Review Topic

QID: 4911
FIGURES:
1

Neurofibromatosis

15%

(678/4501)

2

Holt-Oram Syndrome

2%

(79/4501)

3

McCune-Albright Syndrome

81%

(3664/4501)

4

Fibular hemimelia

0%

(4/4501)

5

Ellis-van-Creveld Syndrome

1%

(42/4501)

ML 2

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PREFERRED RESPONSE 3

(OBQ09.74) A mutation in a G(s) alpha protein (activating G protein that increases cAMP) results in which of the following diseases? Review Topic

QID: 2887
1

Fibrous dysplasia

82%

(1473/1792)

2

Diastrophic dysplasia

6%

(102/1792)

3

Cleidocranial dysostosis

3%

(49/1792)

4

Osteogenesis imperfecta

5%

(85/1792)

5

Achondroplasia

4%

(79/1792)

ML 1

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PREFERRED RESPONSE 1

(OBQ07.26) The G-protein coupled family of receptors play a crucial role in transmembrane cytokine signaling. Point mutation in the Gs-alpha subunit of this receptor is responsible for a specific bone/soft tissue disease. Which of the following radiographs corresponds to this disease? Review Topic

QID: 687
FIGURES:
1

Figure A

16%

(260/1601)

2

Figure B

3%

(55/1601)

3

Figure C

5%

(87/1601)

4

Figure D

8%

(132/1601)

5

Figure E

66%

(1051/1601)

ML 2

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PREFERRED RESPONSE 5

(OBQ09.21) All of the following are characteristic of McCune-Albright syndrome EXCEPT? Review Topic

QID: 2834
1

Caused by a mutation in G(s)alpha subunit

10%

(208/2046)

2

Cafe-au-lait spots

4%

(90/2046)

3

Polyostotic fibrous dysplasia

4%

(90/2046)

4

Multiple neurofibromas

77%

(1572/2046)

5

Precocious puberty

4%

(80/2046)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 4
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ARTICLES (14)
VIDEOS (1)
CASES (4)
Topic COMMENTS (13)
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