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Ankylosing spondylitis is a chronic inflammatory disease, which principally affects the spine, and the joints between the spine and the pelvis. The inflammation occurs at the junction between the bone and ligaments. Some erosion of bone occurs at the site of inflammation. A process of healing follows resulting in new bone formation at this site. With repeated episodes of inflammation followed by new bone formation the affected area gradually becomes immobile.
Eventually, it causes the affected vertebrae to join or fuse together. The acronym AS (Ankylosing Spondylitis) is frequently used in medical literature.
The cause of AS is still unknown. It belongs to the autoimmune family of diseases. The term 'autoimmune' means that the body's defence mechanism or immune system is turned against various tissues within the body itself. This is a reverse of the immune system's usual stance, which is to defend the body against attack such as infection. Through this process the immune system inflicts damage on various body tissues. The trigger factor that initiates this process is not fully understood.
A gene called HLA-B27 occurs in over 90% of patients suffering from ankylosing spondylitis. However, not every person possessing this gene will develop the condition.
The commonest symptom of AS is joint pain. It usually begins in the lower end of the spine in a joint known as the sacroiliac joint. This is the junction between the sacrum, or lower end of the spine, and the pelvis. The second most commonly affected area is the thoracic or chest part of the spine. The hips, knees and ankles are occasionally affected although any joint has the potential of being affected by AS.
Some people experience mild symptoms involving the lungs, heart, eyes or bowel. These difficulties are generally not serious or progressive and generally subside with simple symptomatic measures.
The course of the condition is variable since it is subject to remission and relapse. People generally feel worse after a period of prolonged rest. Early morning stiffness is a common complaint. Some people experience night sweats and fatigue. In the early stages some people lose some weight. A minority of people will progress to experience more severe forms of AS with resulting significant disability and pain.
It is unlikely that a diagnosis of ankylosing spondylytis would be made on a first visit to the GP. It may take some time for a clear pattern of disease to emerge. A history of back pain persisting for more than three months should alert one to the possibility of AS.
Sometimes it will be necessary to be referred to a consultant for further evaluation. Diagnosis is based on the symptom pattern and physical signs. Blood tests and x-rays will be required to assist in diagnosis. If a pattern emerges consistent with the diagnosis of ankylosing spondylitis then the doctor will usually test for the presence of the HLA-B27 gene.
The objectives of treatment are to relieve pain and modify the course of the disease. The principal concern is to limit the extent of joint damage thereby maintaining the maximum level of movement in affected joints.
Among the treatments offered are:
Ankylosing spondylitis usually affects men between the ages of 15 and 35. It is very rarely seen in women. A family history of AS is a positive risk factor for the disease.
It is not possible to prevent ankylosing spondylitis. However, early diagnosis assists in modifying the progression of the disease and limits the extent of permanent disability.
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