Port Elizabeth, South Africa – Fibrous dysplasia is a benign tumour-like condition in which normal bone is replaced by structurally poor fibro-osseous lamellar bone. It occurs as a result of an early embryonic postzygotic activating mutation of the GNAS gene which manifests clinically in a wide spectrum of disease. Fibrous dysplasia occurs in a monostotic form with single bone involvement, or polyostotic form with multiple bones of the axial, appendicular and craniofacial skeleton involved. McCune-Albright syndrome occurs when the polyostotic form of the disease is associated with extraskeletal manifestations including endocrinopathies, café-au-lait skin lesions and/or intramuscular myxomas. Presentation is dependent on the extent of tissue involvement and ranges from an asymptomatic incidental radiographic finding to symptomatic disease with pain, deformity, pathological fracture, malignant transformation or sequelae of associated endocrinopathies. Diagnosis is usually made on the basis of typical clinical and radiological findings but further histological and molecular testing may be required in more atypical presentations. Management by a multidisciplinary team is crucial to achieve satisfactory patient outcomes. An individualised approach to patient care is advised. Endocrinopathies need to be managed as they can worsen orthopaedic deformities and bone pain, and increase risk of fracture. Medical management includes analgesia and intravenous bisphosphonates. Denosumab is a new emerging treatment option but needs further research. Surgical management is aimed at relieving bone pain, preventing fracture and correcting deformities that have led to mechanical abnormalities especially around the proximal femur. Intramedullary load-sharing devices with whole bone fixation are a preferred option. Bone grafting can be considered as an adjunct to mechanical stabilisation but is rarely used in isolation. Although rare, worsening pain and lesion expansion should alert the clinician to possible malignant transformation. Prognosis for patients with fibrous dysplasia is dependent on the location and extent of the disease.
