The presence of a specific tissue component known as HLA-B27 has been increasingly noted in individuals with ankylosing spondylitis.

This fact has led to the theory that the condition is hereditary. However, merely the presence of HLA-B27 in individuals does not indicate that the individual is sure to be affected. Factors such as environmental stresses seem to have a role in initiating the disorder in such individuals.

Frequent infection of the bowel or urinary tract may also be the triggering factor.

This disorder mainly affects the areas of the bones where the tissues and other structures that constitute the joint get attached.

One initiated the disorder results in inflammation in these areas, which is followed by a series of cell reactions that eventually results in replacement of the soft-tissues of the joints by bone.¹