It is a member of the group of the spondyloarthropathies which includes reactive arthritis ( previously known as Reiter's syndrome ), psoriatic arthritis, inflammatory bowel disease-related spondyloarthritis and undifferentiated SpA. The shared features of this group are:
- Inflammatory arthritis in a characteristic pattern, often of the sacroiliac joints and / or the axial skeleton.
- Asymmetric peripheral joint involvement, usually in the lower limbs
- Inflammation of ligament or tendon insertions ( enthesitis )
- An association with the presence of HLA-B27
- A higher incidence of uveitis and psoriasis
It is more common in men than women and usual onset is at 20 - 30 years.
Chronic back pain is common which is inflammatory in nature in 5 % of younger patients. It is useful to note that 50% of inflammatory back pain are due to AS. The current definition for inflammatory back pain is:
- Onset in patients aged less than 50 years
- Chronic back pain of greater than three months' duration; plus two or more of the followings:
-morning stiffness lasting longer than 30 minutes
-pain and stiffness relieved with exercise but not with rest
-alternating buttock pain
-being awoken by pain in the second half of the night
In the setting of inflammatory back pain the presence of any of the additional features makes the diagnosis of AS more likely.
-pain and stiffness relieved with exercise but not with rest
-alternating buttock pain
-being awoken by pain in the second half of the night
In the setting of inflammatory back pain the presence of any of the additional features makes the diagnosis of AS more likely.
- History of uveitis/inflammatory bowel disease/family history
- Restricted spinal movements
- Sacroilitis
- Pulmonary fibrosis/cardiac involvement
There are small number of people who do not respond to NSAID or are contraindicated to NSAID and they have poorer prognosis.
Investigation:
Radiological changes: According to New York Criteria from 1984, a patient is classified as having AS if he or she has a definite radiographic sacroiliitis plus one of the following:
Inflammatory markers are not useful for diagnosis of AS. 40% of people with AS will never have an elevated CRP/ESR level. However, in patients who has elevated inflammatory markers, changes in levels may reflect changes in disease activity. Persistent elevation in markers seem to reflect a worse prognosis.
HLAB-27: The diagnosis of AS relies on clinical evaluation and radiological findings. Only one blood test can add further weight to the diagnosis and that is the test for surface antigen HLAB-27. This test has a reported sensitivity and specificity of 90%.
Management:
Physiotherapy is universally accepted part of the mangement of any patient with AS.
NSAID are the first line drug therapy for all patients with AS. It improves axial and peripheral pain, as well stiffness and overall function.
Corticosteroid: for patients with extra-axial symptoms, corticosteroid injections are useful for enthesitis and peripheral arthritis.
Radiological changes: According to New York Criteria from 1984, a patient is classified as having AS if he or she has a definite radiographic sacroiliitis plus one of the following:
- Inflammatory back pain
- limitation of range of movement in hte lumbar spine in the saggital and frontal planes
- limited chest expansion
Inflammatory markers are not useful for diagnosis of AS. 40% of people with AS will never have an elevated CRP/ESR level. However, in patients who has elevated inflammatory markers, changes in levels may reflect changes in disease activity. Persistent elevation in markers seem to reflect a worse prognosis.
HLAB-27: The diagnosis of AS relies on clinical evaluation and radiological findings. Only one blood test can add further weight to the diagnosis and that is the test for surface antigen HLAB-27. This test has a reported sensitivity and specificity of 90%.
Management:
Physiotherapy is universally accepted part of the mangement of any patient with AS.
NSAID are the first line drug therapy for all patients with AS. It improves axial and peripheral pain, as well stiffness and overall function.
Corticosteroid: for patients with extra-axial symptoms, corticosteroid injections are useful for enthesitis and peripheral arthritis.
Patients with peripheral arthritis may be managed with sulfasalazine but methotrexate and leflunamide has very little evidence to be used.
TNF-alpha inhibitors: Infliximab, Etanercept and Adalimumab
Patients with AS who failed to respond to NSAIDs may require treatment with TNF-alpha inhibitors. The clinical response to TNF alpha inhibitor is quite rapid. The degree of improvement is related to the duration of the disease before treatment: the earlier it is treated the greater the potential response.
TNF - alpha inhibitor is not without significant complications. They are contraindicated in active infection and may increase the rate of tuberculosis.
Patients with AS who failed to respond to NSAIDs may require treatment with TNF-alpha inhibitors. The clinical response to TNF alpha inhibitor is quite rapid. The degree of improvement is related to the duration of the disease before treatment: the earlier it is treated the greater the potential response.
TNF - alpha inhibitor is not without significant complications. They are contraindicated in active infection and may increase the rate of tuberculosis.
Before TNF-alpha inhibitors are prescribed to patients with AS, it is recommended that patients are screen for latent tuberculosis.
Etanercept has been associated with an exacerbation of Crohn's disease and adalimumab with development of SLE. Infliximab has been associated with development of psoriasis, peripheral arthritis, SLE and vasculitis.
Criterial for eligibility of PBS benefit for TNF-alpha inhibitors:
-Reduced chest expansion
-Reduced lumbar mobility
Criterial for eligibility of PBS benefit for TNF-alpha inhibitors:
- Documented X ray evidence of sacroilitis
- At least two of the following three criteria:
-Reduced chest expansion
-Reduced lumbar mobility
- Elevated level of ESR > 25 mm or CRP >15
- Failed a minimum three-month trial of two different NSAIDs in conjunction with an appropriate program
- A Bath Akylosing Spondylitis Disease Activity Index of at least four.
- Completed appropriate concomitant exercise program.
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