Ankylosing spondylitis: an overview

Abstract

Ankylosing spondylitis (AS) is a complex, potentially debilitating disease that is insidious in onset, progressing to radiological sacroiliitis over several years. Patients with symptomatic AS lose productivity owing to work disability and unemployment, have a substantial use of healthcare resources, and reduced quality of life. The pathogenesis of AS is poorly understood. However, immune mediated mechanisms involving human leucocyte antigen (HLA)-B27, inflammatory cellular infiltrates, cytokines (for example, tumour necrosis factor alpha and interleukin 10), and genetic and environmental factors are thought to have key roles. The detection of sacroiliitis by radiography, magnetic resonance imaging, or computed tomography in the presence of clinical manifestations is diagnostic for AS, although the presence of inflammatory back pain plus at least two other typical features of spondyloarthropathy (for example, enthesitis and uveitis) is highly predictive of early AS. Non-steroidal anti-inflammatory drugs (NSAIDs) effectively relieve inflammatory symptoms and are presently first line drug treatment. However, NSAID treatment has only a symptomatic effect and probably does not alter the disease course. For symptoms refractory to NSAIDs, second line treatments, including corticosteroids and various disease modifying antirheumatic drugs, are employed but are of limited benefit. Emerging biological therapies target the inflammatory processes underlying AS, and thus, may favourably alter the disease process, in addition to providing symptom relief.

Figure 1

Evolution from undifferentiated spondyloarthropathy (uSpA) to ankylosing spondylitis (AS) in patients with definitive radiological sacroiliitis.⁶⁹ This previously unpublished figure is based on data published by Dr W Mau and is printed with the author's permission.

Figure 2

A biopsy specimen from a patient with acute sacroiliitis shows cellular infiltrate containing activated fibroblasts and lymphocytes that seem to invade a degenerate cartilaginous area.⁹⁴ Reproduced with permission of the author and the copyright holders from reference 94. Copyright © 2000 by the Annals of the Rheumatic Diseases.

Figure 3

Pelvic radiograph of a patient with AS showing sacroiliitis grade II on the right side and grade II–III on the left. This previously unpublished figure is provided courtesy of Dr M Rudwaleit.

Figure 4

Pelvic radiograph of a patient with AS showing bilateral sacroiliitis grade III. This previously unpublished figure is provided courtesy of Dr M Rudwaleit.

Figure 5

Pelvic radiograph (A) showing suspicious changes: a small circumscribed zone of sclerosis of the left sacroiliac joint (sacroiliitis grade I–II) and slightly blurred joint margins of the right sacroiliac joint (grade I). The corresponding MRI (B) of the sacroiliac joints shows contrast enhancement of periarticular bone (oedema) and of the joint space of both sacroiliac joints reflecting acute inflammation (subtraction technique after intravenous application of gadolinium). These previously unpublished figures are provided courtesy of Dr M Rudwaleit.

Figure 6

Diagnostic algorithm for axial SpA (early AS) starting with the assessment of inflammatory back pain. The combination of several typical SpA manifestations results in a high disease probability. This figure will be published in Ankylosing spondylitis: clinical features. In: Hochberg M, Silman A, Smolen J, Weinblatt M, Weisman M, eds. Rheumatology. 3rd ed. London: Mosby: a division of Harcourt Health Sciences Ltd, ©2002. Reproduced with permission from Dr M A Khan and Mosby.