Childhood fibrous dysplasia.

Fibrous dysplasia is a rare, non-malignant bone disorder in which diagnosis may be easy (polyostotic forms) or more difficult (monostotic forms). Complementary radiological examinations (standard X-ray, CT, scintigraphy) are essential to pinpoint the location or locations of bone involvement. In case of diagnostic doubt, bone biopsy screens for GNAS gene mutation. Fibrous dysplasia may be isolated or part of McCune-Albright syndrome. In case of extraosseous involvement, it is essential to investigate the physiology of the various affected tissues (e.g., for phosphate diabetes). International guidelines were issued in 2019, for diagnosis of fibrous dysplasia and McCune-Albright syndrome and for patient management. There is no specific medical treatment for fibrous dysplasia, but appropriate analgesics and biphosphonates can improve quality of life. In fibrous dysplasia, the bone may be fragile, particularly in the femoral neck, leading to limping, bone deformities and pathological fractures. Orthopedic management ranges from simple monitoring for small monostotic lesions in non-weight-bearing areas to invasive surgery with axial correction and preventive osteosynthesis. In children, fibrous dysplasia lesions can be found at birth on histology, but appear progressively until puberty on X-ray. The impact of skeletal growth, with asymmetric growth due to fibrous dysplasia lesions, lower limb length discrepancy and epiphysiodesis, make surgical management complex. Intramedullary nailing is the surgical technique of choice. LEVEL OF EVIDENCE >V: Expert opinion.