Wang et al. found that the serum Dkk-1 concentration was significantly increased in RA patients than in healthy controls and patients affected by other rheumatic diseases; moreover, increasing Dkk-1 levels were associated with bone erosion and correlated with levels of inflammatory markers like serum C-reactive protein levels and erythrocyte sedimentation rates. This evidence concerns the gene DKK1 and rheumatoid arthritis.