Presentation (obstetrics)

Sacroiliitis

Surgery

Dermatology

Psoriatic arthritis

Spondylitis

Ankylosing spondylitis

Arthritis

Internal medicine

Axial spondyloarthritis

Medicine

Psoriasis

Inflammatory arthritis

Disease

Nature Reviews Rheumatology

Ankylosing spondylitis (AS) was first identified in the late 17th century. 250 years later, inflammatory spine disease was recognized to be one of the patterns of psoriatic arthritis (PsA). Isolated spondylitis is rare among patients with PsA, occurring in less than 5% of patients; however, many patients with PsA have axial disease that is concurrent with peripheral arthritis. At the other end of the spondyloarthritis spectrum, psoriasis is observed in 10% of patients with AS. Although axial involvement in PsA can be indistinguishable from axial disease in AS, it can also differ in several respects, raising the question of whether axial PsA and AS (with or without psoriasis) are different clinical presentations of the same disease, or whether they are separate diseases that have overlapping features. In this Review, the clinical presentation, metrology, radiographic characteristics, genetic factors, treatment options and axial prognosis of the two diseases are addressed. The aim of this Review is to capture all available comparisons made to date, to highlight the similarities and differences between AS and axial PsA and to propose a research agenda. Axial disease occurs in psoriatic arthritis (PsA) and ankylosing spondylitis, but questions remain over whether axial PsA is a distinct disease. In this Review, the authors address the current state of knowledge concerning axial PsA and propose a research agenda.

Axial disease in psoriatic arthritis and ankylosing spondylitis: a critical comparison