There is no clarity for the exact cause of ankylosing spondylitis. Experts include AS in the list of autoimmune diseases such as diabetes, psoriasis, rheumatoid arthritis, thyroiditis, etc. Genetic factors are responsible for the development of AS. Human Leukocyte Antigen B27 (HLAB27) gene is present in the bloodstream of the affected patients.
We will try to summarize the probable causes of AS
As mentioned above the HLAB27 gene is present in the bloodstream and there are tests to detect this gene. It cannot be termed as the diagnostic tool as it may not be present in some cases. Alternatively, even if this gene is present then also the person may not be affected. This means that for the development of AS needs other factors as well. A study in the US shows that out of 10% of positive people with HLAB27 the AS affects only 1-2 %.
Positive family history of AS and presence of this gene in your bloodstream makes you more prone for AS.
Autoimmunity can answer many questions related to cause of AS. What triggers this autoimmunity is again a topic of research. Autoimmunity means that the body's defense mechanism mistakingly attacks its own cells and causes inflammation.
When we talk about environmental or external factor responsible to develop autoimmunity or to express the underlying genetic tendency then emotional stress comes first in our mind. Continuous emotional stress may lead to the evolution of AS and it may also act as a maintaining factor.