Spondyloarthritis is a term used to describe a group of related inflammatory diseases that primarily affect the spine and other joints. Ankylosing spondylitis (AS) is a common type of spondyloarthritis.
The main difference between spondyloarthritis and AS is that all cases of AS are a form of spondyloarthritis, but not all cases of spondyloarthritis are AS.
The different types of spondyloarthritis share some similar features and some key differences as well.
This article reviews the differences and similarities between spondyloarthritis and AS.
The Arthritis Foundation defines spondyloarthritis as a broad term that describes several inflammatory diseases that primarily affect the spine and joints in the body.
In addition to joints, spondyloarthritis can affect organs, such as the intestines and eyes.
There are several different types of spondyloarthritis, including:
- reactive arthritis
- psoriatic arthritis
- undifferentiated spondyloarthritis
- enteropathic arthritis, which has an association with inflammatory bowel disease (IBD)
AS, the most common type of spondyloarthritis, often causes pain in the lower back and pelvic area. The pain typically is worst in the morning and during periods of rest but improves as a person moves.
A person may also experience symptoms in other joints, such as the hips, heels, and shoulders.
Over time, a person may develop ankylosis in the spine. This means that new bone growth occurs in the spine, causing sections of the spine to fuse together, which limits mobility.
Spondyloarthritis is a blanket term and refers to several different inflammatory conditions that affect a person’s joints. AS is the most common form of spondyloarthritis.
The difference between each type of spondyloarthritis relates to the primary areas the conditions affect and the underlying immune imbalance. They break down as follows:
- AS: This primarily affects the sacroiliac joints where the spine meets the pelvis.
- Reactive arthritis: This affects large joints, such as the knees, in reaction to certain bacterial infections.
- Psoriatic arthritis: This is often associated with psoriasis, an inflammatory skin condition. The condition primarily affects peripheral joints.
- Enteropathic arthritis: Often associated with IBD, the condition mainly affects the peripheral joints, such as the arms and legs, and spine.
Since AS is a form of spondyloarthritis, they share several features.
Some common traits include:
- having an average age of onset between the ages of 17–45
- having unknown causes, although genes play a role
- sharing similar symptoms
- affecting more areas than just the joints
Since most people living with spondyloarthritis have AS, one of the first symptoms is pain in the lower back and pelvis region, often in the morning.
A person may experience symptoms such as:
- pain in other joints, such as the elbows, knees, shoulders, hips, hands, or ankles
- skin rash, particularly with psoriatic arthritis
- pain or redness in the eyes
- dactylitis, which is swelling and pain in the tendons of the fingers and toes
- enthesitis, which is pain and swelling where the tendons meet the joints
- bloating, pain, or other symptoms in the stomach with IBD
According to the American College of Rheumatology, not all causes of spondyloarthritis are known. However, researchers do have some insight into the cause of several types.
For example, AS is a hereditary condition. Researchers have found over 30 genes that can be associated with AS. The most common predisposing gene is HLA-B27.
A person’s sex may also play a role in the development of AS. Males may have a slightly higher risk of developing the condition, but females have been underdiagnosed.
Regarding enteropathic arthritis, researchers do not know the exact cause. However, they do know that bacteria in the gut can trigger the condition when they enter areas that have been damaged due to inflammation.
Similar to AS, people with the gene HLA-B27 have a higher risk factor of developing enteropathic arthritis.
In addition, a urinary tract infection (UTI) can trigger reactive arthritis.
Finally, some theories suggest that bacteria can be a major trigger of spondyloarthritis. A person may or may not have an obvious history of infection.
A doctor will typically ask several questions about a person’s medical history and perform a physical examination.
Additionally, a doctor may order both blood and visual tests, such as an X-ray, ultrasound, or MRI.
In some cases, a doctor may recommend a person get tested for the presence of HLA-B27. However, since the gene does not necessarily mean a person has spondyloarthritis, they may not request this test for a clinical diagnosis.
Currently, no treatment can cure spondyloarthritis. Treatment can help reduce the severity of symptoms and help slow the progression of the disease.
Some common treatments include:
- physical or occupational therapies
- nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, to help with pain and inflammation
- disease-modifying antirheumatic drugs, which can reduce symptoms and may help prevent joint damage
- antibiotics for some cases of reactive arthritis
- biologics, including tumor necrosis factor (TNF) alpha-blockers and interleukin-17 (IL-17) blockers
AS is the most common form of spondyloarthritis. As a result, it shares several similar causes, symptoms, and treatments to other types of spondyloarthritis, though slight variations between each can exist.
A person should work with a doctor, preferably a rheumatologist, to determine the best treatment plan to help alleviate symptoms, prevent the condition from getting worse, and maintain optimal health.