The major bone homeostasis and remodeling factors include osteoprotegerin (TNFRSF11B), Dickkopf-1 (DKK-1), receptor activator of nuclear factor–kB (RANK) and RANK ligand (RANKL).46,47 In RA, bone erosion is a major associated condition that develops very rapidly. The gene discussed is TNFSF11; the disease is rheumatoid arthritis.