Fibrous Dysplasia

Fibrous dysplasia(FD):- a non-neoplastic tumour-like lesion with developmental anomaly of bone formation due to failure of the production of normal lamellar bone.

• Pathology:- replacement of normal bone & marrow by fibrous tissue & small woven spicules of bone; poorly mineralized trabeculae.

  • Types– 1. Monostotic(80%):  ribs, femur, tibia, skull2. Polyostotic(20%) : in multiple bones.

• Site:- Epiphysis, Diaphysis, Metaphysis.

• Associated conditions:- Sexual precocity, Abnormal skin pigmentation( cafe-au-lait spots), intramuscular myxoma, Thyroid disease-hyperthyroidism,

• McCune Albright syndrome– polyostotic fibrous dysplasia(Unilateral) +  Cutaneous pigmentation + endocrine abnormalities (precocious puberty)

• Mazabrand syndrome– polyostotic fibrous dysplasia + intramuscular myxoma

•Osteofibrous dysplasia– also known as Campanacci disease mainly affecting Tibia & fibula esp. cortices.

  • Risk of malignant transformation(1%):- osteosarcoma/fibrosarcoma/malignant fibrous histiocytoma.

 

  • Clinical Features:-

    • Symptoms:
      •  usu. asymptomatic(incidental finding)
      • sometimes swelling/deformity
      • if fractures- pain
    • Physical examination:
      •  Cutaneous(cafe-au-lait spots)- +/-
        • larger with irregular borders( as compared to neurofibromatosis)
        • usually +nt in  McCune Albright syndrome
      • swelling
  • Radiology: Central lytic lesion with luscent area, Ground glass appearance, Expansile with thinning of cortex may be found, vertebral collapse & kyphoscoliosis, Shepherd’s crook deformity, Rind sign
  • Histology:- ~fibroblast proliferation around islands of woven bone (woven bone without osteoblastic rimming which is present in Osteofibrous dysplasia); trabeculae of osteoid  in fibrous stroma; Mitotic figures

• Conservative treatment: a)Obsevation- for asymptomatic pt.

b) Bisphosphonates- for pt. with extensive disease (polyostotic lesion) with symptoms (reduces pain & bone turn over).

 

• Surgery: Indications- 1. Significant deformity(treated by osteotomy with Int.fixation/ pathological fracture- internal fixation; 2. Significant pain.

-Impending fracture => intramedullary fixation

• Recurrence– high after curettage & BG- so cortical BG/bone graft substitutes preferred over cancellous BG.