Psoriatic arthritis (PsA) is a chronic inflammatory disease affecting joints, and it may manifest as peripheral arthritis, dactylitis, enthesitis, spondylitis, or sacroiliitis. In the great majority of patients, PsA is accompanied by the most frequent psoriatic manifestation--psoriasis vulgaris. The major genetic risk factor for PsA is an HLA-C allele, and in recent genome-wide association studies few other susceptibility loci have as yet been identified. In this issue, Murdaca et al. (2014) describe an association of an intronic single-nucleotide polymorphism at the TNF locus (+489) with PsA, disease severity, and treatment responses to tumor necrosis factor-α blockers.