Several studies have described single nucleotide polymorphisms (SNPs) in osteoprotegerin (OPG), RANK or RANKL, which influence bone mineral density (BMD), or are associated with susceptibility to rheumatoid arthritis, peri-implantitis, and sporadic primary hyperparathyroidism-related lower BMD [9–15]. The gene discussed is TNFRSF11B; the disease is primary hyperparathyroidism.