Consistent with this early finding, BPs have been shown to decrease the expression of the receptor activator of NF-kB ligand (RANKL) and increase the expression of the RANKL decoy receptor osteoprotegerin (OPG) in human osteoblastic cells (Viereck et al., 2002). Here, TNFRSF11B is linked to Bartsocas-Papas syndrome 1.