Ankylosing spondylitis tends to begin between the ages of 20 to 40 and both males and females can be affected.
Clinical manifestations begin in late adolescence or early adulthood, and rarely after the age of 40 years old. Why this age group is most affected is still unknown but it may be due to the inheritance of the HLA-B27 gene.
Despite many studies, it is still unclear how the gene predisposes patients to disease, but it may be due to its effect on how immune cells interact with one another.
