Mutations in genes encoding RANKL, RANK, and OPG lead to hereditary bone diseases in human, such as autosomal recessive osteopetrosis (ARO) [23, 24], familial form of early-onset Paget’s disease of bone (PDB2) [25–27], familial expansile osteolysis (FEO) [26, 28–30], expansile skeletal hyperphosphatasia (ESH) [31], panostotic expansile bone disease (PEBD) [32], and the Juvenile Paget’s disease (JPD, or idiopathic hyperphosphatasia, IH) [32–37]. Here, TNFSF11 is linked to juvenile Paget disease.