Non-radiographic axial spondyloarthritis

By Jonathan Chan, MD, as told by Hallie Levine

Confused about the difference between ankylosing spondylitis, axial spondyloarthritis and non-radiographic axial spondyloarthritis? With so many similar-sounding terms, it can be difficult to know which is which. WebMD turned to rheumatologist Jonathan Chan, MD for answers to some of your most pressing questions. Here’s what you need to know.

What is non-radiographic axial spondyloarthritis?

It’s a type of inflammatory arthritis known as axial spondyloarthritis that affects your spine and sacroiliac joints. These are the joints that connect your lower spine to your pelvis. It causes pain in the lower back, hips, and buttocks. There are two classes of axSpA: non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS). If you have the former, it means doctors can’t see damage to your joints on an X-ray. But once they start seeing them, your condition has become AS.

It’s more common than many of us realize. Up to 6% of people with chronic back pain are ultimately diagnosed with nr-axSpA. The earlier you are diagnosed, the better your prognosis and the less likely you are to progress to AS.

What causes nr-axSpA?

We don’t know for sure, but family history seems to play a big part. You are at higher risk if a first-degree relative, such as a parent or sibling, already has the disease. While there are around 30 genes linked to its development, one in particular — the human leukocyte antigen, HLA-B27 — appears to particularly increase your risk. Age can also play a role, as symptoms usually begin in your 20s. Smoking is also a risk factor. But unfortunately I still have many patients who have never smoked, eat right and exercise and still develop nr-axSpA.

Will my nr-axSpA become ankylosing spondylitis?

That is hard to say. It is actually debatable whether it is even the same disease or not. We know that some people with nr-axSpA will later develop ankylosing spondylitis. A 2018 study found that about 5% of patients do so after 5 years and nearly 20% after 10 years. There appear to be some risk factors for progression, such as the presence of the HLA-B27 gene or blood tests showing elevated levels of c-reactive protein, a substance that indicates inflammation. But frankly, from a treatment perspective, there is no difference. All therapies that we would use for ankylosing spondylitis act on nr-axSpA and vice versa. The key is to get an early diagnosis. It can often last more than 10 years.

What are the symptoms of nr-axSpA and why is it sometimes overlooked?

Most often it is back, buttock and hip pain. But it is different than traditional back pain. It doesn’t come on suddenly, but happens slowly, over weeks, months, or even years. It gets better with activity, not rest, and can be intense enough to wake you up at night. You may also notice morning stiffness that takes a while to go away. In about 40% of cases, patients develop other inflammatory diseases such as uveitis or inflammatory bowel disease.

The problem is that back pain is a common complaint among patients and the average family doctor may not realize that it could be due to inflammatory arthritis. But I would say if you develop chronic low back pain before age 45 or already have an inflammatory condition, you should ask your doctor for a referral to a rheumatologist.

How is nr-axSpA diagnosed?

There are three things your doctor needs to make a diagnosis:

• An X-ray of the SI joint
• A blood test to check for the HLA-B27 gene
• An MRI of the area

If an X-ray shows no joint damage, but an MRI shows active inflammation, then you most likely have a diagnosis of nr-axSpA. If the X-ray shows damage, you will be diagnosed with ankylosing spondylitis.

How is nr-axSpA treated?

There are three broad categories including:

physical therapy and exercise. It is best to start as soon as possible after diagnosis. It’s very important to do core exercises to take pressure off your back, along with cardiovascular exercises and strength training. It’s a good idea to see a physical therapist, even if you’re already exercising regularly, to make sure you’re exercising properly and in a way that doesn’t cause further joint damage. Since nr-axSpA can “freeze” the spine, posture training is also important.

Nonsteroidal anti-inflammatory drugs (NSAIDs). Prescription drugs like celecoxib (Celebrix) can help control pain and stiffness, but these usually only work in the very early stages. When most patients come to me, they are not enough.

biologics. This is a class of drugs that have truly revolutionized the treatment of inflammatory arthritis. They work by blocking proteins that cause inflammation. We usually start with a group of drugs known as anti-tumor necrosis factor drugs (anti-TNF drugs or TNF inhibitors), such as infliximab, etanercept, or adalimumab. But when patients don’t respond to or cannot tolerate these drugs, we try another form of biologics known as anti-interleukin-17 therapy, such as secukinumab (Cosentyx) and ixekizumab (Taltz). With all of these options, many patients with nr-axSpA are able to control symptoms and halt disease progression.