GNAS and Fabry disease: Regarding the mechanism, the current view is that GNAS mutations can cause a disruption in GTPase activity and constitutive Gs-α activation (Robinson et al., 2016), which leads to the overproduction of cAMP that causes hyperproliferation and incomplete differentiation of marrow stromal cells to abnormal osteoblasts in FD and inhibits osteoblasts-specific genes as well as stimulating cytokines that promote bone resorption by osteoclasts (Riddle and Bui, 2013).