Fibrous Dysplasia

Key Features

• Dysplastic fibrous tissue replacement of the medullary canal is accompanied by the formation of metaplastic bone in areas with fibrous dysplasia

• Three forms of the disease are recognized

  • Monostotic

  • Polyostotic

  • Polyostotic with endocrine disturbances (precocious puberty in females, hyperthyroidism, and hyperadrenalism [Albright syndrome])

Clinical Findings

• Characteristics of lesions

  • May be asymptomatic

  • Begins centrally within the medullary canal, usually of a long bone, and expands slowly

• Pain, if present, is probably due to pathologic fractures

• In females, endocrine disturbances may be present in the polyostotic variety and are associated with café au lait spots

Diagnosis

• If metaplastic bone predominates, the contents of the lesion have the density of bone

• The disease is often asymmetrical, and limb length disturbances may occur as a result of stimulation of epiphysial cartilage growth

• Marked deformity of the bone may result, and a shepherd's crook deformity of the upper femur is a classic feature of the disease

Treatment

• No treatment is needed if the lesion is small and asymptomatic

• Curettage and bone grafting are indicated if the lesion is large and produces or threatens pathologic fracture