Types of Spondyloarthritis
Spondyloarthritis, also called spondyloarthropathy, spondylitis or SpA, is a general term that encompasses several different arthritis conditions that cause joint inflammation. In most cases, SpA affects the joints in the spine, although in some people it can affect other joints in the body.1,2
The types of spondyloarthritis include1,3:
- Ankylosing spondylitis – The most common type of SpA, ankylosing spondylitis (AS) mainly affects the joints in the spine and primarily begins in the sacroiliac joints, which are located where the hip bones (or pelvic bones) meet the base of the spine.
- Psoriatic arthritis – Psoriatic arthritis often occurs in people with psoriasis and can cause inflammation in the joints, changes in the nails, and fatigue.
- Inflammatory bowel disease (IBD) associated arthritis – People who have Crohn’s disease and Ulcerative Colitis can have a spondyloarthritis in addition to bowel disease.
- Reactive arthritis – Often preceded by an infection, reactive arthritis is acute and tends to occur for a limited time, although some people will develop other forms of chronic arthritis.
- Juvenile spondyloarthritis – Juvenile spondyloarthritis refers to SpA that begins in childhood. Children tend to have more symptoms in their peripheral (arm and leg) joints than adults.
- Undifferentiated spondyloarthritis – In undifferentiated spondyloarthritis, people have symptoms that don’t fit one of the other categories of SpA.
How SpA differs from other types of arthritis
SpA differs from rheumatoid arthritis because people with SpA do not have antibodies such as rheumatoid factor show up on their bloodwork. For this reason, SpA are characterized as seronegative spondyloarthropathies. (Seronegative refers to the factor not being present in a blood test.)1,2
SpA also differs from other arthritis conditions because in addition to the joints, it involves the locations where the ligaments and tendons attach to the bones, called entheses. The inflammation of entheses is called enthesitis, and they are tender spots that may be referred to as “hot spots.”2,4
Can someone have ankylosing spondylitis and rheumatoid arthritis at the same time?
In the past, AS was commonly misdiagnosed as rheumatoid arthritis (RA). However, newer tests can differentiate between these two diseases. It is extremely rare for someone to have both AS and RA, although it can occur.5
Criteria for SpA
The criteria for diagnosing SpA comes from the Assessment of SpondyloArthritis International Society (ASAS), which has defined criteria for axial SpA (those affecting the spine) and for peripheral SpA (those affecting other parts of the body, like the arms and legs).6
The criteria require that a person has had back pain for at least 3 months and age of symptoms beginning at less than 45 years and one of the following6:
- Inflammation of the sacroiliac joints seen on imagining plus at least one SpA feature
- HLA-B27 marker plus at least two SpA features
SpA features include inflammatory back pain (Pain that started gradually, is typically worse with rest and better with exercise), arthritis, heel enthesitis, uveitis (inflammation of the eye), dactylitis (inflammation of the fingers or toes, creating a sausage-like appearance), psoriasis, Crohn’s disease or ulcerative colitis, good response to non-steroidal anti-inflammatory drugs (NSAIDs), family history of SpA, and elevated C-reactive protein (a protein associated with inflammation that is found through a blood test).6
Peripheral SpA is defined as having arthritis, enthesitis, or dactylitis and one additional type A feature or two additional type B features. Type A features are psoriasis, inflammatory bowel disease, a preceding infection, HLA-B27 marker, uveitis, or inflammation of the sacroiliac joints on imaging. Type B features are arthritis, enthesitis, dactylitis, inflammatory back pain in the past, and a positive family history of SpA.6
SpA may also be referred to as radiographic or non-radiographic axial spondyloarthritis. Radiographic SpA means that inflammation and/or joint damage is visible on imaging, such as x-ray or magnetic resonance imaging (MRI). The term radiographic SpA is also used in place of AS, and these terms refer to the same condition. Non-radiographic means that the joints appear normal on imaging, but they have other symptoms of SpA.7,8