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Ankylosing spondylitis: The difficulty and importance of early diagnosis -- Knowledge of early disease and a high index of suspicion are required.

Article Excerpt
Byline: KARA PRESCOTT, MD, JOEL D. TAUROG, MD

ABSTRACT: The physical findings and radiological features of ankylosing spondylitis (AS) often shown in textbooks typically are late disease manifestations. However, early diagnosis requires knowledge of the early manifestations. Low back pain is the usual first manifestation; physicians distinguish between inflammatory and noninflammatory back pain as a key to recognizing AS. The findings on physical examination include limitation of lumbar spinal motion and decreased chest expansion. MRI helps detect early sacroiliitis and spondylitis.

In most patients, plain x-ray films of the sacroiliac joints should be obtained first. No laboratory test is diagnostic of AS. About 90% of patients with AS have inherited the HLA-B27 gene. Significant advances have been made in the development of questionnaires and other clinical assessments. (J Musculoskel Med. 2007;24:163-173)

Ankylosing spondylitis (AS) is a chronic, progressive inflammatory disorder that primarily affects the spine but also the peripheral joints and other sites. AS has a strong genetic basis and is part of the spectrum of spondyloarthritis conditions (Table 1),1 which have an estimated overall prevalence of about 1% in whites. Largely independent but interactive risk factors may include the HLA-B27 gene, genes that predispose to inflammatory bowel disease (IBD), and genes that predispose to psoriasis.

The primary symptoms of AS are spinal pain and stiffness, along with fatigue. They typically start in early adulthood but may start in childhood. The diagnosis historically has been made about 3 times more often in men than in women, but this ratio appears to be decreasing gradually. As many as 40% of persons with AS experience attacks of acute anterior uveitis2; aortic valve disease or third-degree heart block may occur in a few patients. Many patients experience disability, and mortality is probably increased with AS.

The pathogenesis of AS is poorly understood, but the fundamental lesion appears to be chronic inflammation at sites of attachment of cartilage, tendons, ligaments, and synovium to bone. Early diagnosis is important for proper management but can be difficult. The physical findings and radiological features of AS often shown in textbooks typically are late disease manifestations, but irreversible deformities often are already present at diagnosis. Early diagnosis requires knowledge of the early disease manifestations and a high index of suspicion. Further complicating early diagnosis, the only validated criteria for a formal diagnosis of AS currently in widespread use, the modified New York criteria (Table 2),3 are insensitive in early AS. In recent years, early changes have been found to be detectable by MRI.

Appropriate patient education and physical therapy, if instituted early, may help prevent debilitating deformity in patients with AS.4 During the past 5 years, biologic therapy with tumor necrosis factor a (TNF-alpha) antagonists has revolutionized treatment and made possible significant reduction of symptoms and further reduction or prevention of disability and deformity.

In this article, we summarize the key points that help physicians make an early diagnosis of AS to allow for early institution of appropriate therapy. We also provide illustrative case studies.

CLINICAL HISTORY

The concept of inflammatoryback pain

Although AS is somewhat uncommon, low back pain (LBP)-the usual first manifestation of AS-is quite common. The differential diagnosis for LBP includes many inflammatory and mechanical causes, such as...