Philip J Mease, Jacqueline B Palmer, Mei Liu, Arthur Kavanaugh, Renganayaki Pandurengan, Christopher T Ritchlin, Chitra Karki, Jeffrey D Greenberg

We analyzed the characteristics of patients with psoriatic arthritis (PsA) with and without axial involvement in the US-based Corrona Psoriatic Arthritis/Spondyloarthritis Registry. All patients were included who had PsA and data on axial involvement, defined as physician-reported presence of spinal involvement at enrollment, and/or radiograph or magnetic resonance imaging showing sacroiliitis. Demographics, clinical measures, patient-reported outcomes, and treatment characteristics were assessed at enrollment. Of 1530 patients with PsA, 192 (12.5%) had axial involvement and 1338 (87.5%) did not. Subgroups were similar in sex, race, body mass index, disease duration, presence of dactylitis, and prevalence of most comorbidities. However, patients with axial involvement were younger and more likely to have enthesitis, a history of depression, and more frequently used biologics at enrollment. They were also more likely to have moderate/severe psoriasis (body surface area ≥ 3%, 42.5% vs 31.5%) and significantly worse disease as measured by a lower prevalence of minimal disease activity (30.1% vs 46.2%) and higher nail psoriasis scores [visual analog scale (VAS) 11.4 vs 6.5], enthesitis counts (5.1 vs 3.4), Bath Ankylosing Spondylitis Disease Activity Index (4.7 vs 3.5) scores, Bath Ankylosing Spondylitis Functional Index (3.8 vs 2.5) scores, C-reactive protein levels (4.1 vs 2.4 mg/l), and scores for physical function (Health Assessment Questionnaire, 0.9 vs 0.6), pain (VAS, 47.7 vs 36.2), and fatigue (VAS, 50.2 vs 38.6). Presence of axial involvement was associated with a higher likelihood of moderate/severe psoriasis, with higher disease activity and greater effect on quality of life. These findings highlight the importance of monitoring patients with PsA for signs of axial symptoms or spinal involvement.