Ankylosing spondylitis is a form of painful, ongoing joint inflammation (chronic inflammatory arthritis) that primarily affects the spine. Early symptoms of ankylosing spondylitis typically begin between the ages of 15 and 30. Most commonly, affected individuals first experience chronic back pain and stiffness. This pain worsens with rest or inactivity, and tends to be relieved with physical activity or exercise.
Pain in ankylosing spondylitis results from inflammation of the joints between the pelvic bones (the ilia) and the base of the spine (the sacrum). These joints are called sacroiliac joints, and inflammation of these joints is known as sacroiliitis. The inflammation gradually spreads to the joints between the vertebrae, eventually involving the whole spine, causing a condition called spondylitis. Over time, back movement gradually becomes limited as the bones of the spine (vertebrae) fuse together. This progressive bony fusion is called ankylosis. These fused bones are prone to fracture.
Ankylosing spondylitis can involve other joints as well, including the shoulders, hips, and, less often, the knees. As the disease progresses, it can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe deeply.
Ankylosing spondylitis affects the eyes in more than 30 percent of cases, leading to episodes of eye inflammation called acute iritis. Acute iritis typically affects one eye at a time and causes eye pain and increased sensitivity to light (photophobia). Rarely, ankylosing spondylitis can also cause serious complications involving the heart, lungs, and nervous system. Six to 10 percent of people with ankylosing spondylitis have additional inflammatory disorders such as psoriasis, which affects the skin, or uclerative colitis or Crohn disease, which both affect the digestive tract.
Ankylosing spondylitis is part of a group of related diseases known as spondyloarthritis. In the United States, spondyloarthritis affect 3.5 to 13 per 1,000 people. Ankylosing spondylitis appears to be more common in certain indigenous populations in North America, Europe, and Asia.
Ankylosing spondylitis is likely caused by a combination of genetic and environmental factors, most of which have not been identified. However, researchers have found variations in several genes that influence the risk of developing this disorder.
The HLA-B gene provides instructions for making a protein that plays an important role in the immune system. The HLA-B gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). The HLA-B gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. A normal variant of the HLA-B gene called HLA-B27 significantly increases the risk of developing ankylosing spondylitis. Although some people with ankylosing spondylitis have the HLA-B27 variant, most people with this version of the HLA-B gene never develop the disorder. (Conversely, this condition can occur in people without the HLA-B27 gene variant.) It is not fully known how HLA-B27 increases the risk of developing ankylosing spondylitis.
Variations in several additional genes, including ERAP1, IL1A, and IL23R, have also been associated with ankylosing spondylitis. Although many of these genes play critical roles in the immune system, it is not fully known how variations in these genes affect a person's risk of developing ankylosing spondylitis. Changes in genes that have not yet been identified also likely affect the chances of developing ankylosing spondylitis and influence the progression of the disorder. Researchers are working to identify these genes and clarify their role in ankylosing spondylitis.
Although ankylosing spondylitis can occur in more than one person in a family, it is not a purely genetic disease. Multiple genetic and environmental factors likely play a part in determining the risk of developing this disorder. As a result, inheriting a genetic variation linked with ankylosing spondylitis does not mean that a person will develop the condition, even in families in which more than one family member has the disorder. For example, studies show that about 75 percent of children who inherit HLA-B27 from a parent with ankylosing spondylitis do not develop the disorder.
Other Names for This Condition
- axial spondylarthritis
- Bechterew disease
- Marie-Struempell disease
- Spondylarthritis ankylopoietica
- Spondylitis ankylopoietica
- Spondyloarthritis ankylopoietica
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Research Studies from ClinicalTrials.gov
Scientific Articles on PubMed
- Akkoç N, Yarkan H, Kenar G, Khan MA. Ankylosing Spondylitis: HLA-B*27-Positive Versus HLA-B*27-Negative Disease. Curr Rheumatol Rep. 2017 May;19(5):26. doi: 10.1007/s11926-017-0654-8. Review. Citation on PubMed
- Bittar M, Yong WC, Magrey M, Khan MA. Worldwide Differences in Clinical Phenotype of Axial Spondyloarthritis. Curr Rheumatol Rep. 2021 Sep 29;23(10):76. doi: 10.1007/s11926-021-01043-5. Review. Citation on PubMed
- Brown MA. Breakthroughs in genetic studies of ankylosing spondylitis. Rheumatology (Oxford). 2008 Feb;47(2):132-7. Epub 2007 Nov 22. Review. Citation on PubMed
- International Genetics of Ankylosing Spondylitis Consortium (IGAS), Cortes A, Hadler J, Pointon JP, Robinson PC, Karaderi T, Leo P, Cremin K, Pryce K, Harris J, Lee S, Joo KB, Shim SC, Weisman M, Ward M, Zhou X, Garchon HJ, Chiocchia G, Nossent J, Lie BA, Førre Ø, Tuomilehto J, Laiho K, Jiang L, Liu Y, Wu X, Bradbury LA, Elewaut D, Burgos-Vargas R, Stebbings S, Appleton L, Farrah C, Lau J, Kenna TJ, Haroon N, Ferreira MA, Yang J, Mulero J, Fernandez-Sueiro JL, Gonzalez-Gay MA, Lopez-Larrea C, Deloukas P, Donnelly P; Australo-Anglo-American Spondyloarthritis Consortium (TASC); Groupe Française d'Etude Génétique des Spondylarthrites (GFEGS); Nord-Trøndelag Health Study (HUNT); Spondyloarthritis Research Consortium of Canada (SPARCC); Wellcome Trust Case Control Consortium 2 (WTCCC2), Bowness P, Gafney K, Gaston H, Gladman DD, Rahman P, Maksymowych WP, Xu H, Crusius JB, van der Horst-Bruinsma IE, Chou CT, Valle-Oñate R, Romero-Sánchez C, Hansen IM, Pimentel-Santos FM, Inman RD, Videm V, Martin J, Breban M, Reveille JD, Evans DM, Kim TH, Wordsworth BP, Brown MA. Identification of multiple risk variants for ankylosing spondylitis through high-density genotyping of immune-related loci. Nat Genet. 2013 Jul;45(7):730-8. doi: 10.1038/ng.2667. Epub 2013 Jun 9. Citation on PubMed
- Khan MA, Haroon M, Rosenbaum JT. Acute Anterior Uveitis and Spondyloarthritis: More Than Meets the Eye. Curr Rheumatol Rep. 2015 Sep;17(9):59. doi: 10.1007/s11926-015-0536-x. Review. Citation on PubMed
- Khan MA, van der Linden S. Axial Spondyloarthritis: A Better Name for an Old Disease: A Step Toward Uniform Reporting. ACR Open Rheumatol. 2019 Jul 11;1(5):336-339. doi: 10.1002/acr2.11044. eCollection 2019 Jul. Citation on PubMed
- Khan MA. An Update on the Genetic Polymorphism of HLA-B*27 With 213 Alleles Encompassing 160 Subtypes (and Still Counting). Curr Rheumatol Rep. 2017 Feb;19(2):9. doi: 10.1007/s11926-017-0640-1. Review. Citation on PubMed
- Mauro D, Thomas R, Guggino G, Lories R, Brown MA, Ciccia F. Ankylosing spondylitis: an autoimmune or autoinflammatory disease? Nat Rev Rheumatol. 2021 Jul;17(7):387-404. doi: 10.1038/s41584-021-00625-y. Epub 2021 Jun 10. Review. Citation on PubMed
- Nancy Z, Yan L, Hui S, Paul B, Liye C. From the Genetics of Ankylosing Spondylitis to New Biology and Drug Target Discovery. Front Immunol. 2021 Feb 17;12:624632. doi: 10.3389/fimmu.2021.624632. eCollection 2021. Review. Citation on PubMed
- Navarro-Compán V, Sepriano A, El-Zorkany B, van der Heijde D. Axial spondyloarthritis. Ann Rheum Dis. 2021 Dec;80(12):1511-1521. doi: 10.1136/annrheumdis-2021-221035. Epub 2021 Oct 6. Review. Citation on PubMed
- Qaiyum Z, Lim M, Inman RD. The gut-joint axis in spondyloarthritis: immunological, microbial, and clinical insights. Semin Immunopathol. 2021 Apr;43(2):173-192. doi: 10.1007/s00281-021-00845-0. Epub 2021 Feb 24. Review. Citation on PubMed
- Robinson PC, van der Linden S, Khan MA, Taylor WJ. Axial spondyloarthritis: concept, construct, classification and implications for therapy. Nat Rev Rheumatol. 2021 Feb;17(2):109-118. doi: 10.1038/s41584-020-00552-4. Epub 2020 Dec 23. Review. Citation on PubMed
- Rosine N, Rowe H, Koturan S, Yahia-Cherbal H, Leloup C, Watad A, Berenbaum F, Sellam J, Dougados M, Aimanianda V, Cuthbert R, Bridgewood C, Newton D, Bianchi E, Rogge L, McGonagle D, Miceli-Richard C. Characterization of Blood Mucosal Associated Invariant T (MAIT) cells in Axial Spondyloarthritis and of resident MAITs from control axial enthesis. Arthritis Rheumatol. 2022 Feb 14. doi: 10.1002/art.42090. [Epub ahead of print] Citation on PubMed
- Rudwaleit M, van der Heijde D, Landewé R, Listing J, Akkoc N, Brandt J, Braun J, Chou CT, Collantes-Estevez E, Dougados M, Huang F, Gu J, Khan MA, Kirazli Y, Maksymowych WP, Mielants H, Sørensen IJ, Ozgocmen S, Roussou E, Valle-Oñate R, Weber U, Wei J, Sieper J. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009 Jun;68(6):777-83. doi: 10.1136/ard.2009.108233. Epub 2009 Mar 17. Erratum in: Ann Rheum Dis. 2019 Jun;78(6):e59. Citation on PubMed
- van der Linden SM, Khan MA, Li Z, Baumberger H, Zandwijk HV, Khan K, Villiger PM, Brown MA. Factors predicting axial spondyloarthritis among first-degree relatives of probands with ankylosing spondylitis: a family study spanning 35 years. Ann Rheum Dis. 2022 Mar 11. pii: annrheumdis-2021-222083. doi: 10.1136/annrheumdis-2021-222083. [Epub ahead of print] Citation on PubMed
- Zhao SS, Pittam B, Harrison NL, Ahmed AE, Goodson NJ, Hughes DM. Diagnostic delay in axial spondyloarthritis: a systematic review and meta-analysis. Rheumatology (Oxford). 2021 Apr 6;60(4):1620-1628. doi: 10.1093/rheumatology/keaa807. Citation on PubMed