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Article Excerpt
ABSTRACT: Ankylosing spondylitis is characterized by inflammation of the axial skeleton. It usually affects the sacroiliac joints and the spine but may also affect peripheral joints. The pathogenesis is uncertain, but the HLA-B27 haplotype gene is most likely associated. Men are affected more frequently than women. Symptoms generally begin in late adolescence or early adulthood; low back pain almost invariably occurs. A detailed clinical history is important, especially in differentiating between mechanical and inflammatory causes of back pain. Diagnosis can be difficult and is often delayed; obtaining x-ray films of sacroiliac joints is necessary. Physical therapy is the mainstay of treatment, although drug therapy can be used to relieve symptoms and improve function. Common complications include osteoporosis and iritis.
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Ankylosing spondylitis (AS) is a chronic systemic inflammatory disorder affecting the axial skeleton--the sacroiliac joints and the spine. Less commonly, it affects peripheral joints, including the hips, shoulders, and knees. The principal pathology is an enthesopathy (inflammation at the point of insertion of tendon, ligament, or joint capsule into bone). Extra-articular features may include acute iritis, mucocutaneous lesions, apical pulmonary fibrosis, aortic valve disease, and heart block.
AS is an unusual inflammatory arthritis in that it affects young persons, usually men, most of whom are engaged in full-time work. The diagnosis is often delayed, resulting in patients being denied effective treatment, sometimes until irreversible structural changes have occurred. It is therefore important to maintain a high index of suspicion, particularly if the history suggests inflammatory rather than mechanical back pain, and to request radiography of sacroiliac joints. Treatment, primarily physical therapy, is effective in most patients who have AS.
In this article, we describe the possible causes of AS; the clinical presentation; various aspects of patient evaluation; and approaches to effective treatment, including physical therapy, drug therapy and, if needed, surgery. We also discuss management of selected complications of the disease.
PATHOPHYSIOLOGY
The pathogenesis of AS is uncertain, but genetic factors play an important role. More than 90% of patients with AS carry the HLA-B27 haplotype, compared with an overall population prevalence of about 7%. The study of HLA-B27 transgenic rats, which develop a disease similar to human AS, has greatly advanced recent understanding of AS. Twin studies suggest that non-HLA genes may also be important: the concordance rate in identical twins is about 50% to 75%, compared with only 13% to 20% in fraternal twins who are both HLA-B27-positive.
The prevalence of AS in the United States is about 0.1% to 0.9%; men are affected more frequently than women by a ratio of about 3:1. Overall sibling risk is about 5.9%. HLA-B27-positive siblings have a risk of about 12%. In one report, disease did not develop in any sibling of an HLA-B27-negative proband or in any HLA-B27-negative sibling of an HLA-B27-positive proband. (1) HLA-B27 is thus almost essential for inheritance of the disease, although sporadic cases may occur in its absence.
Microbial triggers are clearly implicated in other HLA-B27-related diseases, such as reactive arthritis, which can be triggered by Chlamydia, Salmonella, Shigella, Yersinia, or Campylobacter infections. The role of infection in AS is less clear. In the transgenic model of AS referred to above, presence of gut flora is essential for development of disease: rats raised in a germ-free environment remain healthy.
CLINICAL FEATURES
Symptoms of AS begin in late adolescence or early adulthood. Low back pain almost invariably occurs and presumably reflects early in volvement of sacroiliac joints. The characteristics of AS pain differ in several aspects from the more usual mechanical pain (Table 1). The pain is usually dull and poorly localized; it may radiate down the thigh and, rarely, beyond the knee. Coughing, sneezing, and twisting may worsen the pain.
Unilateral symptoms are frequent in the early stages of AS, but progression to bilateral pain after a few months is usual. Spreading of pain up to...
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