![]() ![]() Juvenile ankylosing spondylitis can occur as well. ![]() AS occurs five times more commonly in men than in women. The prevalence of AS is between 0.2% and 0.8% in whites. Many of the manifestations of AS are the result of an exaggerated reparative response to this inflammatory process. The resulting inflammatory cellular infiltrates target cortical bone, cartilage, and ligaments adjacent to fibrocartilaginous and synovial joints. Cytokines, such as interleukin-10, as well as genetic and environmental factors, are also believed to play a role. It has been postulated that some external antigenic agent, possibly a microbial agent, may trigger an abnormal response by T-cells to the HLA-B27/peptide complexes that form in these patients. HLA-B27 is believed to play an important role in initiating and perpetuating the T-cell–mediated immune process, which leads to the manifestations of AS in most patients with this disorder. Approximately 1% of patients who are HLA-B27 positive will develop a rheumatoid factor–negative spondyloarthropathy (ankylosing spondylitis, psoriatic arthropathy, Reiter’s disease, and arthritis of inflammatory bowel disease). HLA-B27 is a genetically encoded antigenic protein found on the surface of leukocytes in some persons. Of all patients with ankylosing spondylitis, 95% are HLA-B27 positive compared with 8% of control white populations 5% of patients with clinical and imaging manifestations of AS are HLA-B27 negative, as in the patient described earlier. The socioeconomic impact of AS on the patient, her family, and on the healthcare system in general cannot be understated. This is a complex, often debilitating condition with insidious onset and a variable degree of involvement in the spine. 8-2, 8-4, and 8-5 ).Īnkylosing spondylitis (AS), also called Marie-Strümpell disease, is a seronegative (rheumatoid factor-negative) disorder causing sacroiliitis, enthesopathy, and spondyloarthropathy, with variable peripheral joint involvement. The intervertebral discs are heterogeneous on MR secondary to intradiscal calcification or ossification (see Figs. The nerve rootlets are adherent to the posterolateral aspect of the thecal sac in and adjacent to the arachnoid diverticula giving a “vacant” thecal sac appearance consistent with chronic arachnoiditis. There is diffuse lumbar dural ectasia and multiple arachnoid diverticula eroding the lamina at several lumbar levels (see Figs. Syndesmophytosis and bilateral SI joint fusion are demonstrated on the radiographs and magnetic resonance (MR) images ( Figs. There is calcification of the intervertebral discs and posterior interspinous and supraspinatus ligaments. The vertebral bodies have a squared off configuration and vertebral body syndesmophytes are visible at all lumbar and visualized lower thoracic levels. ![]() 8-1 and 8-2 ) reveal symmetric fusion of both sacroiliac (SI) joints and a bamboo configuration of the spine. Anteroposterior (AP) and lumbar spine radiographs ( Figs. ![]()
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