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Diagnosis and differential diagnosis of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults

David T Yu, MD
Astrid van Tubergen, MD, PhD
Section Editor
Joachim Sieper, MD
Deputy Editor
Paul L Romain, MD


Axial spondyloarthritis (axSpA) is a potentially disabling inflammatory arthritis of the spine, usually presenting as chronic back pain, typically before the age of 45. It is often associated with one or more of several articular features, including synovitis, enthesitis, and dactylitis. It may also be associated with several non-articular features; these include uveitis, psoriasis, and inflammatory bowel diseases. Patients frequently carry the gene for human leukocyte antigen (HLA)-B27, and patients with active inflammatory disease often have evidence of an elevated acute phase response. (See "Clinical manifestations of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults".)

Patients with axSpA are classified as having either of two subtypes of axSpA: ankylosing spondylitis (AS) or nonradiographic axSpA (nr-axSpA). Patients with AS exhibit radiographic abnormalities consistent with sacroiliitis, but such findings are not evident on plain radiography in nr-axSpA. Instead, in patients with nr-axSpA, the diagnosis is supported by evidence of active inflammation of the sacroiliac (SI) joints on magnetic resonance imaging (MRI) and/or a combination of other findings. In clinical practice, distinction between these forms of axSpA in an individual patient has limited impact on management and may not be relevant, although the classification is of interest for epidemiologic and other investigative purposes. (See 'Nomenclature and classification' below.)

The diagnostic evaluation, diagnosis, and differential diagnosis of AS and nr-axSpA will be reviewed here together as axSpA. The clinical manifestations, treatment, and pathogenesis of this disorder are discussed separately. (See "Clinical manifestations of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults" and "Assessment and treatment of ankylosing spondylitis in adults" and "Pathogenesis of spondyloarthritis".)


Historically, spondyloarthritis (SpA, formerly termed spondyloarthritides or spondyloarthropathies) has been regarded as a family of arthritis that includes ankylosing spondylitis (AS), undifferentiated SpA, reactive arthritis, psoriatic arthritis, juvenile SpA, and arthritis and spondylitis associated with inflammatory bowel diseases, including Crohn disease and ulcerative colitis [1]. AS has been regarded as the prototype of SpA, and the majority of publications on SpA focus on AS. (See "Clinical manifestations and diagnosis of peripheral spondyloarthritis in adults" and "Reactive arthritis" and "Clinical manifestations and diagnosis of psoriatic arthritis" and "Spondyloarthritis in children" and "Clinical manifestations and diagnosis of arthritis associated with inflammatory bowel disease and other gastrointestinal diseases".)

The term axial spondyloarthritis (axSpA) became standard nomenclature in 2009, based upon a multinational study of SpA by the Assessment of SpondyloArthritis International Society (ASAS) classifying SpA broadly into two groups [2,3]:

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Literature review current through: Nov 2017. | This topic last updated: Jul 12, 2017.
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