Although we do not have a definitive explanation for the frequent occurrence of concave margins in fibrous dysplasia, two hypotheses may be proposed: (1) Imbalanced osteoclastic activity; GNAS mutation that characterizes FD disrupts osteoblastic function and upregulates cytokines—especially interleukin-6—that stimulate osteoclastic bone resorption. This evidence concerns the gene IL6 and Fabry disease.