The majority of people with this condition (96%) carry the HLA-B27 gene (whereas only 8% of the general population have this gene). The problem is that if you do have this gene it makes you susceptible to an auto-immune reaction if you have an overgrowth of the Klebsiella bacteria in your gut because the immune system confuses this microbe with the gene (which it has similarities with). Professor Ebringer found this bacteria is far more common in those with ankylosing spondylitis and they have higher levels of antibodies to it.
If you reduce the levels of these bacteria then typically the ankylosing spondylitis improves or disappears. The way to do this is to remove the food for these bacteria which is starch. This means stopping bread, pasta, cakes, potatoes and rice.