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Fibrous dysplasia of bone
Fibrous dysplasia of bone is a congenital non-hereditary benign bone disease, where normal bone is replaced by a fibrous-like tissue with immature osteogenesis.
- Synonym(s): -
- Prevalence: Unknown
- Inheritance: Not applicable
- Age of onset: Childhood
- ICD-10: Q78.1
- OMIM: -
- UMLS: C0016063
- MeSH: D005357
- GARD: 6444
- MedDRA: 10016664
Prevalence is difficult to estimate, due to frequent asymptomatic lesions.
Bone lesions are mono- or polyostotic and may be associated with bone pain and fragility, leading to fractures. In some patients or bone sites, they are hypertrophic, and responsible for neurological complications.
A common molecular defect, i.e. activating mutations of the GNAS gene, encoding the alpha-subunit of the Gs protein in target cells, is responsible for bone cell alterations as well as for the involvement of other cells/tissues bearing the same molecular defect (melanocytes, endocrine cells). These mutations affect only somatic cells and are therefore not hereditary.
Imaging and, when necessary, histology are the cornerstones of the diagnosis.
Antenatal diagnosis is not appropriate for this disease.
Genetic counselling is not very useful, except for reassuring the patients.
Management and treatment
The conventional therapeutic approach is essentially symptomatic (analgesics) and orthopaedic (prevention and treatment of bone complications). Recent publications have focused attention on pamidronate, which rapidly relieves bone pain in most patients, and progressively increases bone mineralization in osteolytic areas in about half of the patients. Tubular phosphate wasting is common and should be treated with phosphate supplement and calcitriol.
The prognosis should improve with therapeutic advances, but this remains to be properly evaluated.
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