• Also Known As:
  • AS
  • Rheumatoid Spondylitis
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What is ankylosing spondylitis?

Ankylosing spondylitis is a form of arthritis that affects the spine. The term is derived from two Greek words meaning “bent spine” and “inflammation.” Ankylosing spondylitis is a chronic condition that causes painful inflammation of the joints between the vertebrae in the spine, and between the spine and pelvis. In advanced cases, the vertebrae may fuse together, further limiting movement and resulting in a hunched over posture. Occasionally, ankylosing spondylitis can involve other joints or more rarely, organs in the body, such as the heart and lungs.

Ankylosing spondylitis affects men more often than women and is usually diagnosed in late adolescence or early childhood. There does appear to be a genetic component to ankylosing spondylitis, which has to do with an antigen called HLA-B27. Although many people who have the HLA-B27 antigen never develop ankylosing spondylitis, it is considered a significant risk factor. While about 7% of the US population is HLA-B27 positive, 90-95% of those with ankylosing spondylitis are HLA-B27 positive. Only about 5-6% of individuals who are HLA-B27 positive will ever develop ankylosing spondylitis. Research into other risk factors and potential triggers that lead to ankylosing spondylitis is ongoing.

There are several theories regarding the exact reason for the inflammation associated with ankylosing spondylitis. One possibility is that foreign DNA, such as from a virus, may trigger the body’s immune system, but the immune system over-reacts and starts attacking its own cells, leading to chronic inflammation. At this time, the exact cause of the inflammation seen in ankylosing spondylitis is not known. One of the effects of chronic inflammation of the ligaments around the bone, particularly in the spine, is triggering of new bone growth, which can cause individual vertebrae to fuse together. Fusion of the vertebrae can lead to permanent reduced mobility of the spine, as well as stiffening of the rib cage. When the ribcage becomes less flexible, the chest cannot expand as fully as usual, and this lower capacity to take in air causes difficulty with breathing.


About Ankylosing Spondylitis

Signs and Symptoms

Early symptoms of ankylosing spondylitis typically include pain and stiffness in the lower back and hips, which may fluctuate over time and spread to other parts of the body. In about 40% of individuals with ankylosing spondylitis, the eyes develop an inflammation called uveitis which can cause eye pain, sensitivity to light, and blurred vision. Other complications can include problems with the heart and lungs.


Currently, there is no single test that can diagnose ankylosing spondylitis. Diagnosis is typically based on imaging studies and signs and symptoms. Various laboratory may be performed in conjunction with physical examinations and medical history to help support a diagnosis. Testing may include:

  • C-reactive protein (CRP) – to check for the presence of inflammation
  • Erythrocyte sedimentation rate (ESR) – another test for inflammation
  • Complete blood count (CBC) – to check for anemia (a low red blood cell count), which is a complication of the chronic inflammation associated with ankylosing spondylitis, and to check for increased numbers of white blood cells, which is a marker of inflammation
  • HLA-B27 antigen test – to determine if someone has this human leukocyte antigen attached to their cells, which correlates with an increased risk of developing ankylosing spondylitis. The test does not diagnose ankylosing spondylitis, but these results, along with other test results and evaluation of physical signs and symptoms help support or rule out a diagnosis of ankylosing spondylitis.
  • X-rays or other imaging tests – to look for changes in the spine and hips, although it may take several years before characteristic degenerative changes are visible

Early diagnosis allows for interventions that may help to prevent or delay complications of the condition.


Although there is no cure for ankylosing spondylitis, exercise and physical therapy can help relieve some of the joint stiffness and certain medications can be used to help relieve pain and decrease inflammation. Medications used to help relieve pain typically include non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, and indomethacin. Medications used to help limit pain and swelling include disease-modifying antirheumatic drugs (DMARDs) such as methotrexate or sulfasalazine, and corticosteroids like prednisone. Newer drugs are available that target the immune system (immunotherapy). To learn more, see the links in Related Content below.

View Sources

Sources Used in Current Review

MedlinePlus. 2016. Ankylosing Spondylitis. Available online at https://medlineplus.gov/ankylosingspondylitis.html. Accessed 6/10/2017.

UpToDate. 2017. Patient education: disease-modifying antirheumatic drugs (DMARDs – Beyond the Basics). Available online at https://www.uptodate.com/contents/disease-modifying-antirheumatic-drugs-dmards-beyond-the-basics?view=print. Accessed 6/10/2017.

Spondylitis Association of America. 2017. Diagnosis of Ankylosing Spondylitis. Available online at http://www.spondylitis.org/Ankylosing-Spondylitis/Diagnosis. Accessed 6/10/2017.

Stanford Health Care. 2017. Ankylosing Spondylitis Diagnosis. Available online at https://stanfordhealthcare.org/medical-conditions/bones-joints-and-muscles/ankylosing-spondylitis/diagnosis.html. Accessed 6/10/2017.

Sources Used in Previous Reviews

MayoClinic.com. Ankylosing spondylitis. Available online at http://www.mayoclinic.com/health/ankylosing-spondylitis/DS00483. Accessed June 2013.

MedlinePlus Medical Encyclopedia. Ankylosing Spondylitis. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000420.htm. Accessed June 2013.

Genetics Home Reference. Ankylosing spondylitis. Available online at http://ghr.nlm.nih.gov/condition/ankylosing-spondylitis. Accessed June 2013.

Spondylitis Association of America. About Ankylosing Spondylitis. Available online at http://www.spondylitis.org/about/as.aspx. Accessed June 2013.

Momeni, M. et al. Cardiopulmonary Manifestations of Ankylosing Spondylitis. International Journal of Rheumatology, Volume 2011 (2011). Available online at http://www.hindawi.com/journals/ijr/2011/728471/. Accessed July 2013.

MedlinePlus. Ankylosing Sponylitis. Available online at http://www.nlm.nih.gov/medlineplus/ankylosingspondylitis.html. Accessed September 2010.

MayoClinic.com. Ankylosing spondylitis. Available online at http://www.mayoclinic.com/print/ankylosing-spondylitis/DS00483/DSECTION=all&METHOD=print. Accessed September 17, 2010.

Wilfred CG Peh. Ankylosing Spondylitis. eMedicine: Radiology. Last updated March 25, 2009. Available online at http://emedicine.medscape.com/article/386639-overview. Accessed Sept 2010.

AllAboutBackandNeckPain.com. Ankylosing Spondylitis. Available online at http://www.allaboutbackandneckpain.com/understand/ankylosing-spondylitis.asp. Accessed Sept 2010.