Activation of RANK–RANKL signalling plays an important role in inflammatory bone erosion that is observed in rheumatoid arthritis, periodontitis and aseptic loosening of orthopaedic implants.40, 41, 42 The binding of RANKL to its receptor RANK on osteoclast precursor cells activates downstream signalling pathways, including the NF‐κB and MAPK pathways, which are important in osteoclast differentiation and function. The gene discussed is TNFSF11; the disease is periodontitis.