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As in other inflammatory rheumatic diseases, the objective of psoriatic arthritis (PsA) treatment is the achievement of a defined target. Recent recommendations propose aiming for remission or low disease activity; however, a consensual definition of remission is lacking. A state of minimal disease activity (MDA) has been established and is defined by low activity assessed by tender/swollen joint counts, tender entheseal points, Psoriasis Area and Severity Index or body surface area, patient pain and global activity visual analog scale, and functional evaluation by Health Assessment Questionnaire. Since its development, MDA has been used increasingly in studies and clinical trials. In this article, the potential use of MDA as a treatment target in PsA is reviewed. The frequencies of MDA achievement with biologic disease-modifying antirheumatic drugs are summarized based on data from registries, observational studies, and clinical trials. Predictors and the prognostic effect of attaining MDA are also evaluated.

Objective To describe the radiographic phenotype of axial spondyloarthritis (SpA) according to the presence of HLA–B27. Methods An international collaboration compared the radiographic phenotype of axial SpA according to HLA–B27 status. Patients with ankylosing spondylitis (AS) and axial psoriatic arthritis (PsA) were collected. Radiographs were read centrally, blinded to clinical details. The symmetry of the sacroiliac joints and lumbar syndesmophytes and the morphology of syndesmophytes (typical marginal versus atypical chunky), together with the modified Stoke Ankylosing Spondylitis Spine Score and the Psoriatic Arthritis Spondylitis Radiographic Index, were recorded. Results A total of 244 patients with PsA and 198 patients with AS were included. In PsA, 60 patients (25%) were HLA–B27 positive while in AS, 148 patients (75%) were HLA–B27 positive. Patients with HLA–B27 were younger and more often male and had a longer duration of disease. In multivariable logistic regression, HLA–B27 was significantly associated with syndesmophyte symmetry (odds ratio [OR] 3.02 [95% confidence interval (95% CI) 1.38, 6.61]) and marginal syndesmophytes (OR 1.97 [95% CI 1.16, 3.36]) but not with sacroiliac symmetry. Mean radiographic scores were higher for patients with HLA–B27. Conclusion Patients with axial SpA who are positive for HLA–B27 have more severe radiographic damage, more marginal syndesmophytes, and more frequent syndesmophyte symmetry compared to patients who are negative for HLA–B27.