Psoriatic arthritis (PsA) is a chronic immune-mediated disease characterized by psoriatic skin and nail changes, peripheral joint inflammation, enthesitis, dactylitis, and/or axial involvement, either alone or in combination with each other. The presence of axial involvement has been shown to be a marker of PsA severity; however, there is no widely accepted definition of axial involvement in PsA (axPsA) or consensus on how or when to screen and treat patients with suspected axPsA. Chronic back pain is a prominent feature of axPsA and is thought to have a relevant role in early identification of disease. Chronic back pain can be caused by inflammatory back pain (IBP) or mechanical back pain (MBP). However, MBP can complicate recognition of IBP and delay diagnosis of axPsA. While MBP can also be associated with chronic back pain of ≥ 3 months in duration that is typical of IBP, IBP is characterized by inflammation of the sacroiliac joint and lower spine that is differentiated from MBP by key characteristic features, including insidious onset at age < 40 years, improvement with exercise but not with rest, and nighttime pain. This review discusses the differences in identification and management of IBP and MBP in patients with PsA with axPsA. The summary of available evidence highlights the importance of appropriate and timely screening, difficulties and limitations of differential diagnoses and treatment, and unmet needs in axPsA.
Keywords: Diagnosis; Inflammatory back pain; Mechanical back pain; Psoriatic arthritis.
Psoriatic arthritis (PsA) is a long-term disease that may lead to psoriatic changes in skin and nails; inflammation of some joints, including finger and toe joints (dactylitis); inflammation of sites where tendons and ligaments connect to bone (enthesitis); and/or problems in the spine (axial involvement). Approximately 25–70% of patients with PsA have axial involvement (axPsA); this number varies because there is no widely accepted definition for axPsA. Chronic (long-lasting) back pain is a major feature of axSpA and can help doctors recognize axPsA early. Chronic back pain can be caused by inflammatory back pain (IBP) or mechanical back pain (MBP). IBP is described by back pain lasting ≥ 3 months, gradual onset at age < 40 years, improvement with exercise, no improvement with rest, pain at night (with improvement upon getting up), and changes in some laboratory test results. On the other hand, MBP is caused by a physical injury to the lower back. Both IBP and MBP can occur in patients with PsA, but they are treated in different ways. Being able to tell the difference between IBP and MBP is important to make sure that patients receive the right treatment. This review looks at the differences between IBP and MBP, screening for IBP, the difficulties and limitations of diagnosing and treating axPsA, and the needs of patients with axPsA for better diagnosis and treatment.