What is ankylosing spondylitis?

Risk Factors

Individuals between the ages of seventeen and forty-five are most at risk for ankylosing spondylitis, as are individuals whose family members have the disease. The American College of Rheumatology reports that, as of 2012, men are two to three times more likely to develop the disease than women are. Other risk factors include having the HLA-B27 gene and having inflammatory bowel disease, ulcerative colitis, or Crohn's disease.

Etiology and Genetics

The causes of ankylosing spondylitis are not well understood, but it seems clear that both genetic and environmental factors play contributing roles. According to the Spondylitis Association of America, approximately 95 percent of affected Caucasians and 50 percent of affected African Americans carry the gene most related to ankylosing spondylitis, the HLA-B27 gene, but not all individuals who express this gene will develop the disease. For example, while 50 percent of the children of an affected parent will inherit the HLA-B27 gene, only about 5 to 20 percent of them will develop spondyloarthritis.

The HLA-B27 gene is one of a family of genes located at the major histocompatability locus on the short arm of chromosome 6 at position 6p21.3. It encodes a protein that is present on the surface of almost all cells and functions to display protein fragments (peptides) that have been exported from the cell to components of the immune system. If the antigens are recognized as foreign, an inflammatory response is triggered. The conditions under which the HLA-B27 protein initiates an inflammatory response resulting in disease are not clear, and theories range from the improper presentation of peptides to the misfolding of the protein itself.

A number of other genes, including IL23R and ERAP1, have been shown to have an association with ankylosing spondylitis. Both IL23R and ERAP1 also play a role in immune function. As noted by Uta Syrbe and Joachim Sieper in The Autoimmune Diseases (2014), IL23R has also been shown to be involved with inflammatory bowel disease and psoriasis, both autoimmune disorders. Moreover, studies by J. J. Pointon et al., published in 2009, and the Austrolo-Anglo-American Spondyloarthritis Consortium, published in 2010, indicate that the genes ANTXR2, IL-IR2, STAT3, TNFR1, and TNFSF15 may also be linked to ankylosing spondylitis.

Symptoms

The severity of an individual’s symptoms can vary from mild to very severe. Common symptoms may include stiffening and pain (arthritis) of the lower back and the sacroiliac, the joint where the back and hip meet, possibly radiating down the legs. The pain is often worse at night; stiffness is worse in the morning. Symptoms may improve with exercise or activity.

Individuals may occasionally experience pain and stiffness in other joints, including the knees, upper back, rib cage, neck, shoulders, and feet. Another symptom is chest pain, which may suggest heart, heart valve (aortic insufficiency), or lung involvement; eye pain, visual changes, and increased tearing may suggest eye involvement (uveitis). Less common symptoms may include fatigue, loss of appetite or weight loss, fever, and numbness (if arthritic spurs compress the spinal nerves).

Screening and Diagnosis

The doctor will ask about a patient’s symptoms and medical history and will perform a physical exam. Diagnosis is based on common symptoms of ankylosing spondylitis, such as dramatic loss of flexibility of the lower back and spine (limitation of motion of the low back), pain in the lower back, and limited chest expansion when taking deep breaths.

Diagnostic tests may include x-rays of the lower back and hips to check for characteristic changes and occasionally a magnetic resonance imaging (MRI) scan or a computed tomography (CT) scan of the joints involved. Blood tests can check for the HLA-B27 gene marker, anemia, an elevated sedimentation rate, and the presence of other autoimmune markers.

Treatment and Therapy

There is no cure for ankylosing spondylitis. Treatment is aimed at providing education and relieving the symptoms and may include medication, such as nonsteroidal anti-inflammatory drugs (NSAIDs), to control pain and inflammation. Disease modifying anti-rheumatic drugs (DMARDs) or tumor necrosis factor (TNF) alpha blockers may be used if NSAIDs are insufficient. The application of heat and cold can also reduce pain and control swelling.

Physical therapy techniques can prevent progression and worsening of symptoms and may include learning proper posture and the best positions for sleeping. Daily exercise is another treatment and can include abdominal and back exercises (to decrease back stiffness and maintain good posture), stretching exercises, swimming exercises, and breathing exercises (in cases where the rib cage is affected). In severe cases, hip or joint replacement surgery may be needed to relieve pain and restore mobility. In some instances, spinal surgery is needed to allow the person to maintain an upright posture.

Prevention and Outcomes

There are no guidelines for preventing ankylosing spondylitis because the cause is unknown.

Bibliography

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Brown, M. A. “Genetics and the Pathogenesis of Ankylosing Spondylitis.” Current Opinion in Rheumatology 21.4 (2009): 318–23. Print.

Firestein, Gary S., et al., eds. Kelley’s Textbook of Rheumatology. 9th ed. Philadelphia: Saunders/Elsevier, 2013. Print.

National Institute of Arthritis and Musculoskeletal and Skin Diseases. "Ankylosing Spondylitis." National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). National Institutes of Health, Jan. 2013. Web. 17 July 2014.

Reveille, John D. "Spondyloarthritis (Spondyloarthropathy)." American College of Rheumatology. Amer. Coll. of Rheumatology, Nov. 2012. Web. 17 July 2014.

Royen, Barend J. van, and Ben A. C. Dijkmans, eds. Ankylosing Spondylitis: Diagnosis and Management. New York: Taylor, 2006. Print.

Spondylitis Association of America. "Ankylosing Spondylitis & Related Diseases Information." Spondylitis.org. Spondylitis Association of America, 2013. Web. 17 July 2014.

Syrbe, Uta, and Joachim Sieper. "Spondyloarthritides." The Autoimmune Diseases. Ed. Ian R. Mackay and Noel R. Rose. 5th ed. San Diego: Academic/Elsevier, 2014. 537–43. Print.

Toussirot, Eric A. “Management of Ankylosing Spondylitis and Related Spondylarthritis: Established Treatments, New Pharmacological Options, and Anti-TNF Therapies.” Arthritis Research. Ed. Frank Columbus. New York: Nova Biomedical, 2005. Print.