The classic clinical description of ankylosing spondylitis was made in the late 1800s and was refined by the addition of radiographic descriptions during the 1930s. Pathological investigation revealed the importance of enthesitis (inflammation at sites of ligamentous attachment to bone) and synovitis. The identification in 1973 of a very strong association with human leukocyte antigen B27 (HLA-B27) led to heightened awareness of the disorder. The concept of spondyloarthritis was proposed in 1974 to emphasize the interrelatedness of ankylosing spondylitis and several other conditions that had previously been described separately. Spondyloarthritis is currently classified as predominantly axial, affecting the spine, pelvis, and thoracic cage, or predominantly peripheral, affecting the extremities.
This new Review Article summarizes the clinical definition of ankylosing spondylitis and axial spondyloarthritis, discusses the pathogenesis of these conditions, and reviews approaches to management.
Table 1. Current and Classic Classifications of Spondyloarthritis.
Q: Name some features of the inflammatory back pain that characterizes axial spondyloarthritis.
A: Spondyloarthritis is differentiated from other causes of back pain when the nature and pattern of the pain and the age of the patient are considered. The most typical symptom is inflammatory back pain. Such pain is usually dull and insidious in onset and is felt deep in the lower back or buttocks. Another prominent feature is morning back stiffness that lasts for 30 minutes or more, diminishes with activity, and returns after inactivity. Although initially the back pain is intermittent, over time it becomes more persistent. Nocturnal exacerbation of pain is common, particularly during the second half of the night, forcing the patient to rise and move around. Pain is often present in the thoracic spine as well. Cervical involvement typically occurs late but can predominate. Pain in the chest occurs in more than 40% of patients with spondyloarthritis. If the source of the pain is not accurately diagnosed, patients may be subject to unnecessary diagnostic workups for cardiovascular disease or other intrathoracic diseases. Inflammatory back pain occurs in 70 to 80% of patients with ankylosing spondylitis and is relatively uncommon in patients whose pain has another source.
Table 2. Characteristics of Inflammatory Back Pain.
Q: What are the classification criteria for axial spondyloarthritis?
A: In 2009, the Assessment of Spondylo Arthritis International Society (ASAS) formulated classification criteria for axial spondyloarthritis that were based on imaging, clinical, and laboratory criteria. With these criteria, the diagnosis is established in persons who have had back pain for 3 or more consecutive months before reaching 45 years of age, who have had the presence of sacroiliitis confirmed on MRI or plain radiography, and who have at least one clinical or laboratory finding that is characteristic of spondyloarthritis. Alternatively, persons with this history who have a positive test result for HLA-B27 plus two features of spondyloarthritis as detected on clinical examination or laboratory analysis also fulfill the criteria for a diagnosis of axial spondyloarthritis. The various criteria have an additive effect on the certainty of diagnosis. The ASAS criteria for axial spondyloarthritis have been criticized for introducing additional diagnostic heterogeneity, both by including both the imaging and nonimaging diagnostic groups together within the category of nonradiographic axial spondylitis and by including nonradiographic axial spondyloarthritis and ankylosing spondylitis together within the category of axial spondyloarthritis. These criteria will probably undergo further revision in coming years.
Figure 2. Algorithm for the Diagnosis or Exclusion of Axial Spondyloarthritis.
Figure 3. Pathogenic Mechanisms in Axial Spondyloarthritis.
Morning Report Questions
Q: What are some of the extra-articular manifestations of ankylosing spondylitis?
A: Acute anterior uveitis has a lifetime prevalence of 30 to 40% in patients with ankylosing spondylitis. Psoriasis occurs in more than 10% of patients with ankylosing spondylitis, and inflammatory bowel disease in 5 to 10%, with Crohn’s disease being more common than ulcerative colitis. Osteoporosis of the spine and peripheral bones is common in ankylosing spondylitis. The combination of spinal rigidity from the formation of syndesmophytes and osteoporosis within trabecular bone contributes to a spinal fracture rate that is as high as 10% among these patients and is associated with a high risk of devastating spinal cord injury.
Q: How is axial spondyloarthritis managed?
A: Treatment goals for axial spondyloarthritis include reducing symptoms, improving and maintaining spinal flexibility and normal posture, reducing functional limitations, maintaining the ability to work, and decreasing the complications associated with the disease. Nonsteroidal antiinflammatory drugs (NSAIDs), including selective inhibitors of cyclooxygenase 2, are the first-line drug treatment for pain and stiffness. Continuous NSAID treatment is recommended for persistently active, symptomatic disease, with doses adjusted in accordance with the severity of symptoms. For patients whose symptoms are not controlled by NSAID therapy or for whom NSAIDs have unacceptable side effects, the use of tumor necrosis factor (TNF) inhibitors is strongly recommended. In 13 randomized, controlled trials and many open-label studies, five TNF inhibitors — infliximab, etanercept, adalimumab, golimumab, and certolizumab — have produced rapid, profound, and sustained improvement in both objective and subjective indicators of disease activity and patient functioning. Approximately 60% of patients have an adequate and usually sustained response to TNF inhibitors, often with partial or full remission of symptoms. The long-term use of systemic glucocorticoids is relatively contraindicated, partly because of the increased risk of vertebral osteoporosis, but may be unavoidable in some patients with severe uveitis or inflammatory bowel disease. Whether spondyloarthritis is active or stable, patients are advised to follow an active exercise program designed to maintain posture and range of motion.
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