Fibrous Dysplasia

Incidence

• 5 - 20% benign bone lesions
• Relatively common and usually monostotic (80%)
• Affects children and adolescents (10-25 y/o)
• Median age at onset 8 years
• Male more than Female

Clinically

• Ribs are commonest sites (40%)
• Lower limbs more than upper limbs
• Craniofacial; skull deformity
• Epiphyses usually spared
• Monostotic disease almost 50% have an asymptomatic rib lesion
• Polyostotic disease
  • Pain
  • Fracture (85%)
  • Deformity 
  • Skin pigmentation (coast of Maine)

X-Rays

• Ground glass appearance typical
• Shepherds crook deformity of proximal femur
• Variable appearance with expansion of cortex

Pathology

• ? developmental hamartoma
• Bone replaced by firm, whitish tissue of gritty consistency (alphabet soup or chinese letters)
• Vascular tumour with poorly orientated bone trabeculae separated by fibrous tissue
• Bone is woven rather than lamellar and lacks osteoblastic rimming of trabeculae

Treatment

• Monostotic : curettage and grafting, if symptomatic
• Polyostotic : symptomatic treatment
• May require osteotomy for deformity or lengthening / shortening procedures

Prognosis

• Monostotic lesions cease activity at puberty, but may be reactivated by pregnancy
• Polyostotic presents with pathological fracture in 85%
• Rarely show malignant change (<1%), unless after radiotherapy

Albright Disease

• A varaint of Fibrous Dysplasia
• Female more than Male
• Consists of
  • Polyostotic disease (unilateral usually)
  • Skin pigmentation (coast of Maine)
  • Endocrinopathy (Precocious puberty)

Osteofibrous Dysplasia

• Rare variant of Fibrous Dysplasia
• Seen in young children
• Usually affects tibial cortex
• Mostly asymptomatic
• May present with local tenderness or bowing of tibia
• Highly vaiable appearance on X-Ray
• Histology is similar to Fibrous Dysplasia, but has osteoblastic rimming
• No treatment necessary, unless symptomatic