What is it exactly?
Spondyloarthritis is a family of related diseases. It is a chronic, autoinflammatory disease predominantly affecting the axial skeleton (sacroiliac joints and spine) which is why it is often called Axial Spondyloarthritis, abbreviated as axSpA. It used to be called Ankylosing Spondylitis or AS for short.
Spondyloarthritis is an umbrella term that was introduced in 2009 after it was realised that there are different expressions of AS, which often are not identified, and didn’t really even have names. So axSpA cover a diverse disease family that share clinical and genetic features, such as the involvement of the axial skeleton. The expression was introduced in order to unify
(1) less severe forms of spondylitis,
(2) the early phase of ankylosing spondylitis, as well as
(3) ankylosing spondylitis itself into one term.
The most known member of the axial spondyloarthritis disease family Ankylosing Spondylitis, or AS for short, is an acute form, which is probably why it’s better known. It causes an inflammatory stiffening of the spinal column for which there is no known cure. In German and French it is also known as Morbus Bechterew, after the name of the man who first described it. Although it mainly affects the spine, it can impact other joints as well; as well as other parts of the body, most commonly the eyes, the intestine or the skin. It usually starts with pain, particularly the lower back, starting in the early hours of the morning. Pain and stiffness of the affected joints generally worsens over time. In more advanced cases the inflammation can lead to ankyloses – which causes sections of the spine to fuse in a fixed, immobile position. (sources: Swiss Axial Spondyloarthritis Association, Spondylitis Association of America, Versus Arthritis, Wikipedia)