Ankylosing spondylitis (AS) is a chronic or lifelong condition involving the joints in the lower portion of the vertebral or spinal column.
While data regarding the number of people with AS are scant, their prevalence is currently estimated to be around 0.01% to 0.5% of the global population. Calculations using figures from relevant literature approximate that more than one and five million patients are stricken with AS in Europe and Asia, respectively. While such information remains unavailable in the Philippine setting, Filipinos afflicted with the disease have been documented clinically.
The precise cause of AS is yet to be identified, but both a person’s genes and their environment are speculated to play a role in its onset and further worsening. Mutations or variations in more than 60 genes have been associated with AS, the most notable of which are those involving the human leukocyte antigen-B (HLA-B) gene. Like other components of the HLA complex, HLA-B gives instructions for making proteins that help our immune system correctly identify other proteins made by our bodies apart from those generated by invaders (such as viruses, bacteria and parasites). The HLA-B27 variant of this gene is extremely common among those with AS (more than 90% of them) compared to less than 10% of the general population without AS. Nevertheless, having the HLA-B27 variant does not automatically mean that one will eventually develop AS; in fact, roughly 80% of children who inherited HLA-B27 from their parents do not get afflicted with the condition. Furthermore, not all pairs of identical twins with the HLA-B27 variant have AS. Other important risk factors are:
The early manifestation of AS is the inflammation (arthritis) of the sacroiliac joints that connect the base of the spinal column (sacrum) and upper part of the hip or pelvis (ilium). Later on, the inflammation may spread to joints or tissues in the upper regions of the spine and in other parts of the body. “Ankylosing” means joining together, while “spondylitis” means arthritis of the spine. These terms allude that as the disease progresses over time, the inflammation drives the affected joints and smaller bones to “fuse” and harden together, eventually becoming inseparable piece(s) of larger, immobile bone.
Signs and symptoms include:
Diagnosis of AS and further assessment of its severity are made by a physician through medical history-taking, physical examination, imaging (such as x-ray or magnetic resonance imaging/MRI) and blood tests. The treatment goals are to relieve pain and maintain functional range of motion in affected joints, correcting or preventing further deformities in posture, and preventing damage in other organs. With regular guidance from physicians and other health professions, the following interventions may be utilized:
As the precise genetic and environmental triggers for AS have yet to be identified, evidence-based approaches for preventing the onset of AS are lacking.