Axial involvement in psoriatic arthritis: An update for rheumatologists

Psoriatic arthritis (PsA) is a heterogenous, chronic, inflammatory musculoskeletal disease that can lead to peripheral and axial damage and loss of function. Axial involvement occurs in 25% to 70% of patients with PsA, varying greatly depending on its definition, with the key manifestations being sacroiliitis and/or spondylitis. However, there are no agreed-upon classification or diagnostic criteria for axial involvement in PsA and no consensus on treatment paradigms, which complicates management of PsA. There have only been a few studies assessing biologics in patients with PsA with axial involvement, and most treatment plans are based on evidence from patients with axial spondyloarthritis. Rheumatologists therefore face many challenges in the management of axial PsA, including diagnosis, differential diagnosis, and choice of appropriate treatment. In this review, we summarize the clinical presentation, imaging characteristics, differential diagnoses, treatment options, and prognosis of axial PsA, with the aim of increasing rheumatologists' knowledge of this phenotype of PsA and thereby aiding its optimal management.