What is Spondyloarthritis?
Spondyloarthropathies (or Spondyloarthritis) are a family of inflammatory disease that cause arthritis, and are different than other inflammatory arthritides because the can affect the spine and soft tissues such as tendons and ligaments (known as enthesitis). The 4 main spondyloarthropathies are ankylosing spondylitis, psoriatic arthritis, reactive arthritis, and enteropathic arthritis associated with inflammatory bowel diseases (ulcerative colitis and Crohn’s disease).
Ankylosing Spondylitis is the most common condition from this group. Also known as AS, this form of arthritis primarily affects the spine, and can cause chronic pain, discomfort, stiffness, and eventually fusing of the bones, leading to decreased mobility.
Who gets it?
There are several risk factors to be aware of for AS. These include:
Age: Unlike most other forms of arthritis, AS is usually seen in younger people. It usually begins in the teens or 20’s, with typical age of onset anywhere from age 17 – 45
Gender: It is likely to happen in 2 – 3 times more frequently in the males than females, unlike many other rheumatologic conditions
Genetics: Having a family member with AS puts a patient at higher risk of getting it, partly due to an inherited gene known as the HLA-B27 gene. The HLA-B27 gene is actually present in about 8% of healthy individuals in society. Of this 8% of people with a positive HLA-B27 gene, only 2% of them develop ankylosing spondylitis. If you have a first degree relative that is affected and you are HLA-B27 positive, your risk increases to 15 – 20%. Though infrequent, 90% of white AS patients and 50 – 80% of non-white AS patients have a positive HLA-B27.
Race: The highest frequency of this condition is in more northern populations, such as Scandinavians, Alaskans, Siberian Eskimos, and Native American tribes. These populations have a higher prevalence of the HLA B-27 genes, and the prevalence of the disease decreases from north to south as you near the equator. African Americans seem to be affected the least of all races.
What exactly happens in the disease?
It is not completely understood how the condition occurs, but it seems to start after some kind of triggering event in genetically susceptible individuals (HLA-B27 positive). The trigger has been hypothesized to be some type of infection, exposure to an unknown antigen, or molecular mimicry where your body confuses itself with an infecting organism.
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