Types of Spondyloarthritis
Spondyloarthritis (SpA) is an umbrella term for a range of inflammatory conditions that result in arthritis. It may also be referred to as spondyloarthropathy.1 It is not like other kinds of arthritis because it arises where ligaments and tendons attach to bones, in addition to joints where bone meets bone.1
Figure 1. The different types of spondyloarthritis
Under the general umbrella of spondyloarthritis, conditions are broken down further into two categories based on where the symptoms occur: Axial spondyloarthritis (AxSpA) or peripheral spondyloarthritis (pSpA).
Axial vs. peripheral spondyloarthritis
Where symptoms occur in the body can help clinicians make a more accurate diagnosis, especially when it comes to spondyloarthritis.
Axial spondyloarthritis generally affects the spine and pelvic joints, whereas peripheral spondyloarthritis mostly affects the arms and legs. The two conditions affect the body in different areas, thus making them two distinct groups of spondyloarthritis. Each condition has other types of conditions within their grouping as well.
Different types of AxSpA
There are two types of AxSpA:
- Ankylosing spondylitis (AS) / Radiographic axial spondyloarthritis (r-AxSpA)
- Non-radiographic axSpA (nr-AxSpA)
Non-radiographic AxSpA (nr-AxSpA) is when someone has AxSpA and the associated symptoms, but there is no damage to the bones or joints seen on imaging tests.3
Nr-AxSpA can sometimes progress to r-AxSpA, which is also known as ankylosing spondylitis (AS). It doesn’t always progress, but it can.
Ankylosing spondylitis (AS) mainly affects the spine, but other joints can also be affected. In AS, spinal joints become inflamed, causing significant pain that is often chronic. When AS becomes advanced, the inflammation can cause new bone formation, resulting in sections of the spine becoming fused.2 This leads to impaired range of motion and deformity.
As AS progresses, the sacroiliac (SI) joints at the base of the spine are affected, causing pain and stiffness. It is also referred to as radiographic AxSpA (r-AxSpA) because the damage to bones and joints is visible on radiology or imaging tests.
Different types of peripheral spondyloarthritis
There are four types of pSpA:4
- Enteropathic arthritis (EnA)
- Reactive arthritis (ReA)
- Psoriatic arthritis (PsA)
- Undifferentiated spondyloarthritis (USpA)
EnA is a kind of arthritis that not only involves inflammation of the spine or limb joints and also of the bowel.4 This causes symptoms like diarrhea, stomach pain, weight loss, and bloody stool. Inflammatory bowel diseases that arise can include Crohn’s disease, ulcerative colitis, or undifferentiated colitis.4
ReA is usually a temporary condition that resolves itself in 3-12 months.4 Typically, there is an infection somewhere else, like the intestine or urinary tract. Joint inflammation then occurs as a reaction. Symptoms of ReA include inflammation or pain in the joints, skin, eyes, mucus membranes, and genitals.4 This type of arthritis can recur, and in some people ReA is associated with the later development of chronic arthritis.4
PsA causes inflammation and pain in the small joints of the hands and feet, and can include even swelling of a single finger or toe in some people.4 The rash associated with psoriasis is present in most people with PsA. There may also be pain or stiffness of the spine.4
Those with USpA have symptoms that match up with spondyloarthritis, but don’t fit into any one category of SpA.4 They may have a few symptoms but not all of a particular condition, leading to the undifferentiated diagnosis. If you find yourself having some symptoms but not necessarily having all of the symptoms of different types of spondyloarthritis, talk with your doctor.