TY - JOUR T1 - What Is Axial Psoriatic Arthritis? JF - The Journal of Rheumatology JO - J Rheumatol SP - 1611 LP - 1613 DO - 10.3899/jrheum.180802 VL - 45 IS - 12 AU - JOY FELD AU - VINOD CHANDRAN AU - DAFNA D. GLADMAN Y1 - 2018/12/01 UR - http://www.jrheum.org/content/45/12/1611.abstract N2 - Psoriatic arthritis (PsA) is a chronic inflammatory musculoskeletal disease that has 5 disease domains: peripheral arthritis, axial disease, dactylitis, enthesitis, and skin and nail disease1. Only 2–5% of patients with PsA have isolated axial disease; most patients with axial arthritis also have peripheral arthritis2,3,4.The prevalence of axial disease in patients with PsA varies with disease duration, occurring in 25–70% of patients with longstanding PsA3 and in 5–28% of patients with early disease5,6,7,8,9,10,11. These differences suggest that axial disease typically develops at a later stage in the disease course. In the Toronto PsA cohort, 15% of patients with PsA who did not have axial involvement at baseline developed axial PsA during 10 years of followup4. The risk factors for the development of axial disease early in the disease course were presence of HLA-B27, the presence of radiographic damage to peripheral joints, and an increased erythrocyte sedimentation rate (ESR), whereas the risk factors for developing axial involvement later on in the disease course were the presence of nail dystrophy, a high number of radiographically damaged joints, the presence of periostitis, and an increased ESR. Additionally, a family history of PsA reduced axial disease risk early in the disease course4. This study4 highlights the fact that different patients are likely to develop axial disease at different timepoints in their PsA disease course. This poses a significant limitation in studies with a cross-sectional design that identify patients at a single timepoint in their disease course compared to longitudinal studies that can record the changing course of the disease … Address correspondence to Dr. D.D. Gladman, Toronto Western Hospital, University Health Network, 399 Bathurst St., 1E410B, Toronto, Ontario M5T 2S8, Canada. E-mail: dafna.gladman{at}utoronto.ca ER -