GNAS and fibrous dysplasia: In the diagnosis of fibrous dysplasia, a potential biomarker could be the detection of the mutated GNAS1 gene; however, it is a variable parameter due to the coexistence of mutated and wild-type GNAS1 within the lesion, as a result of a genetic mosaicism; it is also a gene that appears to be mutated in different exons in other pathologies [12].