“Somewhere around 5 to 10 percent of individuals with AS also have inflammatory bowel disease (IBD), either Crohn’s disease or ulcerative colitis,” says Joel Taurog, MD, a professor of internal medicine and immunology in the division of rheumatic diseases at the University of Texas Southwestern Medical Center in Dallas. Here’s what you should know about the connection between AS and IBD — including when it’s important to get gastrointestinal (GI) symptoms checked out and how the two conditions can be treated together.
IBD and Ankylosing Spondylitis: What’s the Link?
While a relatively small number of people with ankylosing spondylitis end up being diagnosed with Crohn’s disease or ulcerative colitis, many more — about 50 percent — show signs of inflammation in their GI tract, according to John Miller, MD, a rheumatologist and instructor of medicine in the division of rheumatology at Johns Hopkins Medicine in Baltimore. “Even though a lot of people with AS don’t have overt gut inflammation, there have been studies that looked at stool inflammatory markers,” Dr. Miller explains. “And a large number of patients with AS have GI symptoms. We kind of separate these diseases into discrete boxes, but I think there’s a lot of overlap.” An abnormal immune response in the digestive tract appears to play a role in both Crohn’s disease and ulcerative colitis. The immune system is made up of proteins and cells that normally protect against infection. In IBD, the immune system mistakenly attacks harmless or even beneficial cells as if they are harmful invaders. This immune response is believed to cause the chronic inflammation seen in IBD that damages the gastrointestinal tract and causes symptoms. Miller notes that we currently don’t have a strong understanding of causation when it comes to AS and IBD — whether an altered immune system allows certain bacteria to develop in the GI tract, or whether the growth of certain bacteria leads to an altered immune response in some people. And, in fact, some people develop symptoms of AS in their spine or other joints before they have any GI symptoms, while for others the order is reversed. But what makes some people more susceptible to both AS and IBD in the first place? “The association is largely genetic,” says Dr. Taurog. “Over half of the 30-plus genes that have been identified as susceptibility genes for AS are also susceptibility genes for IBD.”
NSAIDs Used With Caution
In a person with AS who has GI symptoms, doctors would tend to be more cautious about prescribing non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin, ibuprofen (Advil or Motrin), Aleve (naproxen), and others. These drugs may irritate the digestive tract and worsen GI symptoms, and may even lead to new inflammation, according to Miller.
TNF Inhibitors May Help Both IBD and AS
Instead, doctors may be quicker to prescribe biologic drugs called TNF inhibitors in people with AS who have IBD. These drugs can help both conditions by targeting an inflammation-promoting substance called tumor necrosis factor (TNF), which is produced by the immune system. “Some of the anti-TNF therapies that have currently been approved for Crohn’s disease and ulcerative colitis can be used to treat ankylosing spondylitis,” says Ashwin Ananthakrishnan, MBBS, MPH, a gastroenterologist at Massachusetts General Hospital in Boston and an assistant professor of medicine at Harvard Medical School. But not every TNF inhibitor is effective for both conditions, and one drug may be more effective than another in a given person. Remicade (infliximab), Humira (adalimumab), Simponi (golimumab), and Cimzia (certolizumab) are approved as treatments for both AS and IBD. Dr. Ananthakrishnan says that the dosing of these drugs, in some cases, might ordinarily be different for the two conditions, so it’s important for your rheumatologist and gastroenterologist to communicate to decide what dose is appropriate for you. Ananthakrishnan notes that getting effective treatment for both AS and IBD that targets the underlying inflammation — including through biologic therapies like TNF inhibitors — may reduce the need for pain medication like NSAIDs. But for some people, taking an NSAID every now and then as needed doesn’t cause digestive upset or any other problems.
IL-17 Inhibitors Risk Worsening IBD
TNF inhibitors aren’t the only group of biologic drugs that can be used to treat AS. Another group, called IL-17 inhibitors, includes Cosentyx (secukinumab) and Taltz (ixekizumab). But these drugs carry a risk for making IBD symptoms worse in people with Crohn’s disease or ulcerative colitis, and may even lead to new cases of IBD. For some people with AS, though — who don’t have IBD or GI symptoms, and don’t respond well to TNF inhibitors — this may be a risk worth taking to get AS under control, according to Miller.
Bring GI Changes to Your Doctor’s Attention
No matter what therapy you take for AS, “it’s important to bring up GI symptoms like diarrhea, blood in the stool, or bloating after meals” with your doctor, Miller says. This applies to both your initial diagnosis and treatment decisions for AS, and to any new symptoms that develop as time goes on. And, unfortunately, new GI symptoms often do develop in people with AS. “If we see new scan findings or new GI symptoms, it’s not a complete surprise,” says Miller. “Sometimes it’s AS that presents first; sometimes it’s GI symptoms that present first.” Additional reporting by Regina Boyle Wheeler.
