Ankylosing Spondylitis

Overview
  • Ankylosing Spondylitis (AS) is a member of the HLA-B27-associated seronegative spondyloarthropathies typically encountered as ascending lower back pain in a young male adult and characterized by inflammation of the sacroiliac joints (Sacroiliitis). The disease is occasionally associated with IBD and can be complicated by ocular inflammation.
Epidemiology
  • Nearly 95% of patient with AS carry the HLA-B27 and the disease is one of the few diseases of likely immune origin with a predilection for men. Onset is usually during young adulthood between the second and third decades.
Etiology and Pathogenesis
  • AS is a disease of immune origin and is likely the consequence of an as yet unknown trigger is a genetically susceptible host. Whatever the etiology, the hallmark of AS is bilateral inflammation of the sacroiliac joints, termed sacroiliitis. This inflammatory process tends to ascend the spinal column with ossification of the inflammatory tissue, resulting in progressive ascending fixation of vertebrae, visible on radiography as "Bamboo Spine". Characteristically for a spondyloarthropathy, the inflammation of AS largely involves the enestheses, the ligamentous insertions into bones.
Clinical Consequences
  • The hallmark presentation of AS is the gradual onset of progressive bilateral gluteal or low back pain and stiffness in a young adult male that is most severe in the morning with improvement during the course of the day. With time back pain tends to ascend and is associated with progressively reduced mobility. The spine can become quite brittle and prone to fracture, with the disastrous consequence of spinal cord injury. The most common extra-articular manifestation of the disease is ocular inflammation, typically presenting as acute anterior uveitis. Most patients display asymptomatic inflammation of the intestines; however, in a minor subset of patients AS can be associated with IBD, either preceding or following onset of inflammatory bowel disease. When AS is associated with IBD the monicker "Enteropathic Arthritis" is often applied.