In recent years, the OPG/RANKL pathway has been found to play an important role in periodontitis, as mice that over-express RANK exhibited severe alveolar bone loss 16, and periodontal therapy has been shown to reduce the level of RANKL in crevicular fluid, and therefore, decrease the RANKL/OPG ratio 17. The gene discussed is TNFRSF11A; the disease is periodontitis.