Ankylosing spondylitis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Ankylosing spondylitis is a chronic, painful, degenerative inflammatory arthritis primarily affecting spine and sacroiliac joints, causing eventual fusion of the spine; it is a member of the group of the autoimmune spondyloarthropathies with a probable genetic predisposition. Complete fusion results in a complete rigidity of the spine, a condition known as bamboo spine.[1]
Historical Perspective
Ankylosing spondylitis was first recognized as a disease by Galen. In the late nineteenth century (1893-1898), however, the neurophysiologist Vladimir Bekhterev of Russia in 1893, Adolph Strümpell of Germany in 1897, and Pierre Marie of France in 1898, were the first to give adequate descriptions which permitted an accurate diagnosis of AS prior to severe spinal deformity. For this reason, AS is also known as Bechterew Disease or Marie–Strümpel Disease.
Pathophysiology
Ankylosing spondylitis is a systemic rheumatic disease, and is one of the seronegative spondyloarthropathies. About 90% of the patients express the HLA-B27 genotype. Tumor necrosis factor-alpha (TNF α) and IL-1 are also implicated in ankylosing spondylitis. Although specific autoantibodies cannot be detected, its response to immunosuppresive medication has prompted its classification as an autoimmune disease.
Causes
Ankylosing spondylitis needs to be differentiated from strain of lumbosacral joint, osteoarthritis, Forestier's disease among others.
Epidemiology and Demographics
In USA, the prevalence of ankylosing spondylitis is 250 per 100,000 and being a chronic condition, the incidence is low.
Risk Factors
Patients with HLA-B27 variant are at highest risk of developing ankylosing spondylitis.
Natural History, Complications and Prognosis
Ankylosing spondylitis can range from mild to progressively debilitating. In a long-term undiagnosed period, osteopenia or osteoporosis of AP spine may occur, causing eventual compression fractures and a back "hump" if untreated. Due to the fusion of the vertrbrae, paresthesia may develop. Other complications are Aortic regurgitation, Achilles tendinitis, AV node block, amyloidosis and lung fibrosis.
Diagnosis
History and Symptoms
Ankylosing spondylitis typically presents in a young patient with chronic pain and stiffness in lower part of spine. In 40% of cases, ankylosing spondylitis is associated with iridocyclitis (anterior uveitis, also known as iritis) causing eye pain and photophobia (increased sensitivity to light). Other common symptoms are recurring mouth ulcers (aphthae) and fatigue.
Laboratory Findings
There is no direct test to diagnose ankylosing spondylitis. There is increase in C-reactive protein (CRP) and Erythrocyte sedimentation rate (ESR).
X Ray
A clinical examination and X-ray studies of the spine, which show characteristic spinal changes and sacroiliitis, are the major diagnostic tools for ankylosing spondylitis. The findings on X Ray are presence of subchondral erosions, sclerosis, proliferation on iliac side of SI joints and squaring of the vertebral body.
CT
An option for more accurate (and much earlier) diagnosis of ankylosing spondylitis is tomography of the sacroiliac joints. Joint erosions, subchondral sclerosis, and bony ankylosis are better visualized on CT.
MRI
The findings on MRI in a patient with ankylosing spondylitis is synovial enhancement. It is superior to CT in detection of cartilage, bone erosions, and subchondral bone changes. An increased T2 signal correlates with edema or vascularized fibrous tissue.
Other Imaging Findings
Bone scintigraphy may be helpful in selected patients of ankylosing spondylitis with normal or equivocal findings on sacroiliac joint radiographs. The ratio of SI joint to sacral uptake of 1.3:1 or higher of the radionuclides is considered abnormal.
Treatment
Physical therapy and exercise, along with medication, are at the heart of therapy for ankylosing spondylitis. Physiotherapy and physical exercises are clearly preceded by medical treatment in order to reduce the inflammation and pain. NSAIDs, DMARD and TNFα blockers are the major types of medications used to treat ankylosing spondylitis. Surgery can be an option in ankylosing spondylitis in the form of joint replacements, particularly in the knees and hips. Surgical correction is also possible for those with severe flexion deformities (severe downward curvature) of the spine, particularly in the neck, although this procedure is considered risky.
References
- ↑ Jiménez-Balderas FJ, Mintz G. (1993). "Ankylosing spondylitis: clinical course in women and men". J Rheumatol. 20 (12): 2069–72. PMID 7516975.