Systemically increased active levels of RANKL are detected in the sera of SLE patients, and increased local concentrations are found in the synovial joint fluids of RA patients, both of which are positively correlated with disease severity (Carmona-Fernandes et al., 2011; Fonseca et al., 2005). This evidence concerns the gene TNFSF11 and systemic lupus erythematosus.