Additionally, Dkk1 in PsA, like in AS, obtained higher serum levels than in RA and OA; BMP4 and sclerostin were higher in OA; Wnt1, Wnt5b, TGF-β1, and IL-22 were higher in AS; the serum concentration of IL-6 was lower in OA, and higher levels of IL-17 A were seen in OA with respect to the other pathologies. This evidence concerns the gene DKK1 and rheumatoid arthritis.