GNAS and Fabry disease: Fibrous dysplasia (FD) occurs after postzygotic mutations in GNAS and can result in elevated FGF23 secretion by the FD tissue.60 This is particularly pertinent to patients with McCune‐Albright syndrome who can also have other associated endocrinopathies.61 FD can be localized to a single area (monostotic) or be part of a more generalized pattern (polyostotic or panostotic) affecting the craniofacial, axial, or appendicular skeleton.