CTNNAL1 and psoriatic arthritis: By comparing psoriasis patients who did not have psoriatic arthritis and patients with psoriatic arthritis, Patrick et al. [37] identified significant loci overlapping the regulatory elements that encompass genes that are differentially expressed in differentiated osteoblasts, including genes that participate in Wnt signaling, such as RUNX1, FUT8, and CTNNAL1. The proteins in Wnt/β-catenin signaling play essential roles in the development of SpA.