This type of arthritis is similar to ankylosing spondylitis (AS), but it differs in one key respect.
If you’ve been experiencing inflammatory back pain — pain that tends to get worse at night or in the morning, or with inactivity, and that gets better with physical activity — you may have found information about ankylosing spondylitis (AS) as a possible source of your pain, or even been screened for this condition. Yet in many people with symptoms that are typical of AS, X-ray images don’t show definitive signs of the disease, and the search for an accurate diagnosis continues.
If you fall in this camp, it’s possible that you have nonradiographic axial spondyloarthritis (nr-axSpA). The name of this condition doesn’t exactly roll off the tongue, and it’s poorly understood by the general public and even by many doctors. But in recent years, the importance of recognizing and properly treating nr-axSpA has been demonstrated by several studies and supported by clinical recommendations.
Here’s what you should know about nr-axSpA if you think you might have it, or if you’ve been recently diagnosed — including what this diagnosis does and doesn’t mean, and the latest recommendations for treating it.
The Basics of nr-axSpA
Nonradiographic axial spondyloarthritis is a form of arthritis that causes inflammation in your spine and sacroiliac (SI) joints, the area where your spine connects to your hips. It shares this basic description with ankylosing spondylitis (AS), but nr-axSpA was recognized as a disease much more recently — the term was officially defined in 2009, and the first comprehensive treatment recommendations for it in the United States were released in 2015. (1)
What distinguishes it from AS is that with nr-axSpA, “in X-rays of the SI joints, you do not see evidence of chronic inflammation,” says Jean Liew, MD, an instructor and spondyloarthritis researcher in the division of rheumatology at the University of Washington in Seattle.
“That doesn’t mean that there is no inflammation of the SI joints,” Dr. Liew explains. “It’s just that it’s not something that’s been going on long enough that you would see it on [an] X-ray, or it’s to a degree that you wouldn’t see it.”
For decades, the absence of X-ray findings needed to diagnose AS meant that no definitive diagnosis could be made. But as magnetic resonance imaging (MRI) has gained widespread use in healthcare settings since the 1980s, it has become possible to get a more detailed view of inflammation in the SI joints than an X-ray allows.
As more and more doctors found evidence of inflammation in the SI joints using MRI that wasn’t visible on X-ray images, it became clear that this condition needed a name and guidelines for a diagnosis.
Symptoms and Diagnosis of nr-axSpA
Most people with nr-axSpA gradually develop pain and stiffness in their lower back as initial signs of the condition.
“Stiffness is a really important clue that it’s inflammatory back pain,” rather than due to mechanical problems in your spine, says John Miller, MD, an instructor of medicine in the division of rheumatology at Johns Hopkins Medicine in Baltimore.
Inflammatory back pain tends to be “back pain that is duller in nature, that gets worse with lack of movement,” says Liew. “If you’re sleeping, it might wake you up at 4 a.m. and force you to get up and move. And when you do move, the pain improves.”
Another clue that back pain is inflammatory in nature — which often suggests AS or nr-axSpA — is when it responds well to a nonsteroidal anti-inflammatory drug (NSAID), such as Advil (ibuprofen) or Aleve (naproxen), according to Dr. Miller.
Some people with nr-axSpA also develop inflammation in other areas of their body, which are known as peripheral manifestations of the disease. These may include:
- Uveitis (a form of eye inflammation)
- Enthesitis (inflammation where a ligament or tendon attaches to a bone), especially in the heel area
- Gastrointestinal (GI) problems (which may or may not meet criteria to diagnose inflammatory bowel disease, or IBD)
As part of diagnosing nr-axSpA, your doctor will consider your symptoms and possibly ask you whether AS or other inflammatory conditions run in your family. If X-ray findings don’t show that you have AS, you’ll need an MRI to confirm that you have nr-axSpA.
“There’s no blood test that tells us if this is spondyloarthritis or not,” Liew notes, and MRI findings require a certain amount of interpretation — which means that diagnosing nr-axSpA can be like putting pieces of a puzzle together.
“Sometimes it helps to see a rheumatologist that has more advanced training in treating and diagnosing spondyloarthritis,” she suggests, but not every patient has this option readily available.
Miller believes that as a treatment for nr-axSpA, exercise is “hands down the most important thing for someone who hasn’t been diagnosed, or someone who has been.” This is confirmed by official guidelines, he notes, which recommend that "if someone has active inflammatory back pain, an exercise regimen, usually under the guidance of a physical therapist, is part of the initial management.”
Your doctor will also probably prescribe a drug to treat your nr-axSpA. Most likely, the first drug you take will be an NSAID. Certain doses and formulations of NSAIDs, and some specific drugs, are available only by prescription, but it’s also possible that your doctor will recommend an over-the-counter (OTC) option. (2)
NSAIDs “are still first-line treatments,” Miller emphasizes. “There’s been a lot of redirection toward biologic medicines,” but treatment guidelines recommend considering this newer group of drugs when NSAIDs fail to control the disease.
NSAIDs that may be prescribed for nr-axSpA include:
- Indocin or Tivorbex (indomethacin)
- Mobic (meloxicam)
- Voltaren (diclofenac)
- Celebrex (celecoxib)
One downside of NSAIDs is their potential side effects, which often include gastrointestinal irritation — potentially leading to heartburn, stomach inflammation (gastritis), and even gastrointestinal bleeding. They may also contribute to heart or kidney problems over the long term.
If NSAIDs don’t control your nr-axSpA well enough, your doctor may prescribe a biologic drug. Specifically, a class of drugs called TNF inhibitors has been shown to be effective at reducing inflammation in nr-axSpA, including in areas outside your spine.
Only one TNF inhibitor, Cimzia (certolizumab pegol), is currently approved by the U.S. Food and Drug Administration (FDA) to treat nr-axSpA. This happened in March 2019 after a study first published that month by the journal Arthritis & Rheumatology showed that the drug led to major improvement in symptoms after 52 weeks in 47 percent of participants with nr-axSpA who took it, compared with just 7 percent of participants who took a placebo (inactive pill). (3,4)
But treatment guidelines from the American College of Rheumatology don’t recommend one particular TNF inhibitor over another, and doctors are free to prescribe any of them for nr-axSpA. They include:
- Cimzia (certolizumab pegol)
- Enbrel (etanercept)
- Humira (adalimumab)
- Remicade (infliximab)
- Simponi (golimumab)
The latest treatment recommendations for nr-axSpA, updated in October 2019, make clear that “we shouldn’t relegate [nr-axSpA] to lesser or more conservative treatment,” compared with AS, says Liew. That means prescribing biologics “when your patients don’t have a response to anything else, and you know anecdotally that this is what they’re going to respond to.” (5)
Liew looks forward to the results of further clinical trials of biologic drugs for nr-axSpA, “so that we can hopefully get FDA approval soon for all the things that are already approved for AS.”