Environmental or bacterial factors can also be a trigger. HLA-B27 occurs in 90-95% of patients with ankylosing spondylitis, compared to a 6 to 9% incidence in the normal population. The exact role of this antigen is unknown but is believed to act as a receptor for an inciting antigen leading to AS. In addition, a direct relationship between AS and the major histocompatibility human leukocyte antigen (HLA)-B27 has also been determined. Studies have shown factors such as genetic background gene called ( HLA-B27), microbial infection, endocrinal abnormalities and immune reaction related to the occurrence of AS. Although a strong link has been established of complex interactions between genetic background and environmental factors. The etiology of AS is not fully understood. AS is more prevalent within Europe (mean 23.8 per 10,000) and Asia (mean 16.7 per 10,000) than within Latin America (mean 10.2 per 10,000). Less than 5% of cases have an onset of symptoms over the age of 45. The onset of symptoms generally occurs between 20-40 years of age. There is a male to female ratio of 2:1 for radiographic axial spondyloarthritis and of 1:1 for non-radiographic axial spondyloarthritis. In highly advanced cases, the spine can fuse together as a result of the bone formation.Įpidemiology /Etiology ĪS Affects 0.1 to 1.4% of the population. It is a osseous excrescences or bony outgrowths from the spinal ligaments as they attach to adjacent vertebral bodies. Syndesmophytes are one of the main features of spinal structural damage in ankylosing spondylitis. An accumulation of the deposits leads to ossification, starting from the vertebral rim towards the annulus fibrosis and characterised by syndesmophytes. Patients diagnosed with AS form calcium deposits in the ligaments between and around the intervertebral discs. The vertebral column normally exists of 24 vertebrae, joined together by ligaments and separated by intervertebral discs. Eventually, the spine is affected by this inflammation. Subsequently, the inflammation moves to entheses, where ligaments and tendons integrate into the bone. Initially, the sacroiliac joints, situated in the lumbar part of the back, which connect the spine and the pelvis, are damaged. Pain in AS can be caused by sacroiliitis, enthesitis, and spondylitis. Early diagnosis and treatment help to control the pain and stiffness and may reduce or prevent significant deformity. It involves synovial and cartilaginous joints, as well as sites of tendon and ligamentous attachment. It causes a decreased range of motion and, in its advanced stages, can give the spine an appearance similar to bamboo, hence the alternative name "bamboo spine".Īlthough not often recognised, axial spondyloarthritis can also cause peripheral joint pain, particularly in the hips, knees, ankles, and shoulders and neck. Affected joints progressively become stiff and sensitive due to a bone formation at the level of the joint capsule and cartilage. It causes characteristic inflammatory back pain, resulting in structural and functional impairments and a reduction in quality of life. It often causes changes in the sacroiliac joints, apophyseal joints, costovertebral joints, and intervertebral disc articulations. Īxial spondyloarthritis predominantly affects the spine, with inflammatory changes causing pain, stiffness and a loss of motion in the back. Radiographic axial spondyloarthritis is also known as ankylosing spondylitis (AS). Non-radiographic axial spondyloarthritis does not show on x-ray, but there are changes on MRI. Īxial spondyloarthritis is used to describe patients who have both non-radiographic and radiographic axial spondyloarthritis. The ASAS criteria allowed, for the first time, earlier identification of axial spondyloarthritis through magnetic resonance imaging (MRI). The term axial spondyloarthritis has only been used since 2009 when the Assessment of Spondyloarthritis International Society Axial Spondyloarthritis (ASAS) classification criteria was developed.
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