Ankylosing Spondylitis

last authored: Oct 2009, David LaPierre

Introduction

Ankylosing spondylitis is a chronic inflammatory joint disease mainly affecting the spine and the sacro-iliac joints. It usually occurs in the 20's or 30's and affects men more frequently then women, with a 2-3:1 ratio.

It is a seronegative arthritis, and is often seen in association with other arthropathies, including reactive arthritis, psoriatic arthritis, ulcerative colitis, and Crohn's disease.

The Case of...

a simple case introducing clincial presentation and calling for a differential diagnosis. To get students thinking.

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Causes and Risk Factors

AP is strongly associated (90%) with with HLA-B27, which is also associated with reactive arthritis, psoriatic arthritis, and arthritis association with IBD. Together, these are known as seronegative arthritis.

It is believed that HLA-B27 is a marker for immunologic predisposition which needs to interact with one or more infectious triggers.

Male to female ratio is 3:1.

Onset is most common during late adolescence or early adulthood.

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Pathophysiology

AS most commonly affects the SI joints and axial skeleton.

starts in the lower spine and gradually ascends, potentially affecting the entire back. Both synovial (facet and costovertebral) and fibrous (intervertebral discs) joints are affected. Inflammation tends to settle and be replaced by bony ankylosis, or joint fusion. The end stage is a fused spine.

Early disease is characterized by an non-specific inflammatory process involving lymphocytes and plasma cells.

Involvement of non-spinal joints is present in approximately one-third of patients. Aortitis and uveitis can sometimes also occur.

Inflammation of tendinoligamentous insertions is characteristic and can lead to bony spurs during chronic disease, a process known as enthesitis.

Cervical spine fracture and cord injury can occur following relatively minor trauma.

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Signs and Symptoms

Involvement of the SI joint is required for diagnosis.

history
physical exam

History

Low back pain is generally the presenting complaint. It is slowly progressive, with exacerbations and remissions. It tends to be dull and poorly localized at first.

Chronic pain and stiffness are the most common findings.

Extra-articular involvement can include acute iritis, aortitis, aortic fibrosis, pulmonary fibrosis, and neurologic deficits