Ankylosing spondylitis is a chronic autoimmune disease which is characterized by inflammation of the joints between the vertebrae of spine. It may give rise to stiffness and pain in different body parts such as neck, back, jaw and hips and it may involve some other organs such as heart, eyes, kidneys and lungs. This kind of arthritis is more common in males than in females and may affect all age groups. Onset of symptoms may be observed during the 2nd and 3rd decade of life.
Although exact causes of ankylosing spondylitis are not clear, some genetic factors are found to be responsible for this disease. The genetic marker, HLA-B27 is the most significant gene associated with this disorder. Recently, two more genes such as IL23R and ARTS1 are identified which are related to Ankylosing Spondylitis. There are approximately 5-6 genes suspected to be involved with ankylosing spondylitis. A person with the age less than 40 and positive for HLA-B27 gene and having the family history of Ankylosing Spondylitis is at the higher risk of developing this disease.
The major risk factors for ankylosing spondylitis are positive HLA-B27 maker, family history of ankylosing spondylitis and frequent gastrointestinal infections. Unlike other types of arthritis, onset of this disease is more common in younger people between the age group of 17-35. However, it may affect older people as well as children. It is more common in men, but it can also affect the women.
A person with genetic predisposition, immune response mediators and inflammatory bowel disease is at the higher risk of developing this disease. Genetic predisposition is an important risk factor for ankylosing arthritis. About 90% of patients with this disorder are positive for HLA-B27 gene. However, it is possible that a person with HLA-B27 may not develop this disease or a person with ankylosing arthritis does not have this genetic marker. If either parent has HLA-B27gene, there are about 50% chances of passing-on this gene to their child. But, the possibility of developing ankylosing spondylitis in the child is less than 10%.
The underlying chronic inflammation may be triggered by some bacterial infections which can cause the development of ankylosing spondylitis. The excessive immune response to the gastrointestinal bacterial infections such as ulcerative colitis and Crohn’s disease may be responsible for the underlying pathogenesis of ankylosing spondylitis.
Ankylosing spondylitis may be associated with the secretion of cytokines such as TNF-alpha. The secretion of these immune response mediators is because of prolonged immune response to the infection. There may be elevated levels of TNF-alpha in the sacroiliac joints of the patients with ankylosing spondylitis.