Fibrous Dysplasia

In: Endotext [Internet]. South Dartmouth (MA):, Inc.; 2000.


Fibrous dysplasia (FD) is an uncommon mosaic disorder falling along a broad clinical spectrum. It arises from post-zygotic mutations in GNAS, resulting in constitutive activation of the cAMP pathway-associated G-protein, Gsα, and proliferation of undifferentiated skeletal progenitor cells. FD may occur in isolation, or in association with skin pigmentation and hyperfunctioning endocrinopathies, termed McCune-Albright syndrome (MAS). Disease may involve any part or combination of the skeleton, ranging from an isolated, asymptomatic monostotic lesion, to severe polyostotic disease resulting in fractures, deformity, functional impairment, and progressive scoliosis. FD may be diagnosed clinically in patients with polyostotic disease and/or extraskeletal features of MAS; however, biopsy is typically required to diagnose monostotic disease. Management is focused on treating endocrinopathies, preventing fractures, optimizing function, and treating pain. All patients should be evaluated and treated for extraskeletal features of MAS at the time of diagnosis. In particular control of growth hormone excess is important to prevent craniofacial FD expansion, and control of FGF23-mediated hypophosphatemia is important to prevent fracture, deformity, and bone pain. A mainstay of FD treatment is surgical, and practitioners should be aware that techniques and procedures used in other skeletal disorders, such as bone grafting and prophylactic optic nerve decompression, are frequently ineffective in FD. There are currently no medical therapies capable of altering the disease course in FD. Bisphosphonates may be effective in treating FD-related bone pain but are unlikely to impact bone quality or lesion expansion. There is a critical need to develop novel therapies capable of altering the disease activity of FD lesions. Ongoing efforts include developing drugs to target the mutant Gsα, and devising strategies for targeting mutant skeletal progenitor cells. For complete coverage of all related areas of Endocrinology, please visit our on-line FREE web-text, WWW.ENDOTEXT.ORG.

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