Ankylosing spondylitis (AS) has traditionally been considered a disease that affects mostly men — yet in reality, it also affects many women.
“Not missing this diagnosis in women is extraordinarily important,” says Atul Deodhar, MD, a professor of medicine and the medical director of rheumatology clinics at Oregon Health and Science University in Portland.
That’s because even though imaging tests may show less-severe findings in women with AS, “They have the same pain, the same fatigue, the same worsening quality of life, the same disability,” says Dr. Deodhar.
Here are some of the reasons it can be harder for women to get an accurate diagnosis of ankylosing spondylitis, and how to go about making sure your condition is recognized and treated appropriately.
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X-Rays vs. MRI as Diagnostic Tests
Experts believe several factors may explain why it's harder to diagnose ankylosing spondylitis in women. A key reason is that before more sophisticated imaging techniques like magnetic resonance imaging (MRI) were developed, X-rays were the only way to see structural changes in AS — and these changes are seen mostly in men.
Deodhar says that in the earlier stages of AS, X-ray imaging tends to show no signs of disease in men or women.
But as the disease progresses, there are often changes visible in X-ray scans of men with AS. “If you only depend on X-rays, then it’s a men’s disease,” he explains. “In women, the X-rays don’t change as often or as early.”
MRI is now able to show much earlier changes caused by active inflammation in the spine and sacroiliac joints, where the spine meets the pelvis. But accurately diagnosing AS with an MRI scan means that a doctor needs to order the right kind of MRI.
“The typical MRI that is ordered for back pain is the lumbar spine,” says Deodhar — the area of the lower back above the pelvis. But to find evidence of AS, “you need to do MRI of the sacroiliac joints, and if you don’t order that, you will miss these changes.”
Failure to do an MRI scan of the area of the spine where changes due to AS tend to be most visible, he says, is a major reason ankylosing spondylitis is missed in women — even when women experience the same kinds of symptoms as men.
Of course, an AS diagnosis in men can also be missed when doctors don’t order an MRI of the sacroiliac joints.
But another reason for AS misdiagnosis in women is that even with the right imaging, changes on an MRI scan are often subtler in women.
“Women may not present with the definitive radiographic [X-ray] changes” seen in men that show signs of inflammation of the sacroiliac joints, or sacroiliitis, says Deodhar.
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Ankylosing Spondylitis Symptoms in Women
Sometimes, women with ankylosing spondylitis experience the “classic” course of the disease, in which the main symptom is low back pain that tends to get worse with rest and better with activity.
But women also disproportionately have symptoms outside the spine, known as peripheral symptoms.
“Clinicians should suspect the disease in women who complain of back pain,” says Ali D. Askari, MD, the chief of the rheumatology division at University Hospitals Case Medical Center and a professor at the Case Western Reserve University School of Medicine in Cleveland.
But they should also look out for patterns of peripheral symptoms in AS, which may include the following:
- Psoriasis (a skin disorder with red, itchy, scaly patches)
- Eye redness or soreness
- Frequent canker sores (mouth sores)
- Irregular nails
- Painful, swollen joints outside the spine (especially the shoulders and hips)
- Abdominal pain or diarrhea
While the shoulders and hips may be the most common areas of joint pain outside the spine, some women with AS experience pain in other areas, says Deodhar — such as their feet, heels, or knees. In these cases, doctors may suspect a sports injury, especially since many women are young and active when they develop AS.
Another symptom of AS that may be more common in women is enthesitis — inflammation of the areas where tendons, ligaments, and muscles connect to bones.
“We are recognizing that enthesitis is more pronounced in women, and that is very easily confused for fibromyalgia, because they complain of aches and pains everywhere,” says Deodhar. “And enthesitis may not be shown on the X-ray, may not be shown on the MRI.”
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AS Treatment Is as Important for Women as It Is for Men
It would be one thing if the differences in how ankylosing spondylitis presents in women meant that they didn’t need the same treatments as men — but that isn’t the case at all. In fact, even though women don’t tend to show changes in X-rays over time, they’re potentially at even greater risk than men for functional impairment related to AS.
“In men and women with the same amount of disease activity” — measured by C-reactive protein, a blood test for inflammation, as well as by MRI scans and symptoms reported by patients — “women have more functional decline. They have more problems with function and disability,” Deodhar explains.
Treatment options are similar for women and men with AS. Medications for ankylosing spondylitis include nonsteroidal anti-inflammatory drugs (NSAIDs), as well as disease-modifying antirheumatic drugs — namely sulfasalazine — for inflammation in peripheral joints outside the spine.
Biologic drugs like TNF inhibitors and IL-17 inhibitors are the latest addition to the AS treatment tool kit. For both men and women, physical therapy and exercise are considered a core part of AS treatment.
Be Proactive to Get a Correct Diagnosis
Deodhar says that unfortunately for women with AS, getting an accurate diagnosis often requires taking the initiative to ask specifically about ankylosing spondylitis as a possibility. “Primary care physicians may not be aware of this condition,” he notes.
A study that Deodhar and his colleagues presented in November 2020 at the ACR Convergence 2020 conference showed that women with early signs of AS, in particular, often encountered doctors who minimized, overlooked, or misinterpreted signs of inflammatory disease.
“Direct questioning and asking for a referral to a rheumatologist are the ways to ensure accurate diagnosis,” Deodhar emphasizes. “Take matters in your own hands and ask, ‘Could this be the condition?’”
Additional reporting by Kristen Stewart.