Non-Radiographic Axial Spondyloarthritis (nr-AxSpA)
Axial spondyloarthritis (AxSpA) is a chronic disease that causes inflammation in the sacroiliac joints, which is the structure that connects the hips to the spine. This area is called the axial skeleton. Like ankylosing spondylitis (AS), people with this condition often test positive for the HLA-B27 genetic marker, though it's not required to test positive for a diagnosis.
Figure 1. The different types of spondyloarthritis
What is non-radiographic axial spondyloarthritis?
There are two types of axial spondyloarthritis:
- Non-radiographic AxSpA (nr-AxSpA), where there is back pain, but the sacroiliac joints show little or no damage due to inflammation on X-ray or MRI
- Radiographic AxSpA (r-AxSpA), in which the characteristic inflammation and the beginnings of spinal fusion in the sacroiliac joints is visible on X-ray or MRI. This is what's commonly referred to as AS.3
Some doctors believe that non-radiographic AxSpA (nr-AxSpA) is simply a very early stage of ankylosing spondylitis that, if it progresses, will gradually become severe enough to be diagnosed as radiographic AxSpA, and then finally AS.
Not everyone who is diagnosed with the non-radiographic form goes on to develop full-blown AS.4
In fact, one study found that only 10 to 40 percent of people with nr-AxSpA went on to develop AS/r-AxSpA over the course of 2 to 10 years.5
Symptoms of non-radiographic axial spondyloarthritis
The number one symptom of non-radiographic axial spondyloarthritis is back pain that is usually worse in the middle of the night or morning. Symptoms often begin in the teen years or young adulthood, and almost always before age 40.5
This is a type of arthritis caused by the body’s autoimmune response (inflammation) rather than mechanical damage to the joints caused by overuse.1,2 That’s why people with nr-AxSpA tend to feel better after exercise or stretching compared to people with a slipped disc who feel better when they remain still.5
In AxSpA, the sacroiliac area may show signs of irritation on X-ray or MRI, but the area is not yet fully deformed or fused by the long-term, severe inflammation of full-blown ankylosing spondylitis. AxSpA may cause mild pain and stiffness for years and never progress into the more severe form of AS.
Facts about non-radiographic axial spondyloarthritis
- Non-radiographic and radiographic spondyloarthritis are diagnosed equally as often.
- Clinical signs of the disease are about the same (back pain that lasts longer than 3 months).
- Both non-radiographic and radiographic forms seem to respond to treatment at similar rates.
- Women are more often diagnosed with nr-AxSpA.
- An elevated C-reactive protein (CRP) test result is less likely in those with non-radiographic AxSpA.4
Psoriatic arthritis and enteropathic arthritis (arthritis with inflammatory bowel disease) is commonly seen with nr-AxSpA. About 15 percent of people with nr-AxSpA also have uveitis, a painful eye inflammation that causes redness and blurred vision.5
Treatments for non-radiographic axial spondyloarthritis
Like other forms of spondyloarthritis or ankylosing spondylitis, the first recommended treatments are usually a combination of NSAIDs (aspirin, ibuprofen, naproxen, etc.), exercise and physical therapy. If NSAIDs don’t relieve the pain, the next course of action is usually TNF inhibitors. Systemic glucocorticoids are not recommended.6
Overall, the good news is that non-radiographic axial spondyloarthritis seems to be a less severe form of ankylosing spondylitis that responds well to treatment, and while painful, may not ever progress to a more serious and debilitating condition.