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Diagnosis and differential diagnosis of ankylosing spondylitis and non-radiographic axial spondyloarthritis in adults

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


Ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA) are potentially disabling chronic inflammatory conditions affecting the axial skeleton that are manifested by chronic back pain. The onset is typically before 45 years of age. The diagnosis of AS depends upon the presence of plain radiographic abnormalities consistent with sacroiliitis [1], while such findings are not evident on plain radiography in nr-axSpA, where 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 [2]. AS and nr-axSpA can also involve the hips, shoulders, and peripheral joints; extraarticular manifestations, including uveitis, may also be seen. (See "Clinical manifestations of ankylosing spondylitis in adults".)

The name “ankylosing spondylitis” is derived from the Greek root “ankylosis,” meaning stiffening of a joint, and “spondylos,” which refers to a vertebra. “Ankylosing spondylitis” thus refers to the inflammatory disorder associated with fibrous or bony bridging of joints in the spine, including the bridging of one or more intervertebral discs. Other terms used historically for AS include Bechterew’s disease, Marie-Strümpell disease, and rheumatoid spondylitis.

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


Ankylosing spondylitis (AS) is the prototypic form of spondyloarthritis (SpA, formerly termed spondyloarthritides or spondyloarthropathies), a family of disorders characterized by sacroiliitis and spondylitis, inflammation and new bone formation around the entheses (the sites of ligament and tendon insertion into bone), and an association with human leukocyte antigen (HLA)-B27. (See "Clinical manifestations of ankylosing spondylitis in adults".)

Other conditions included historically in the SpA family are undifferentiated SpA; reactive arthritis; psoriatic arthritis; juvenile SpA; and arthritis and spondylitis associated with inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis [1]. (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".)


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Literature review current through: Mar 2017. | This topic last updated: Oct 19, 2016.
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