Inflammatory Bowel Disease and Axial Spondyloarthritis

Reviewed by: HU Medical Review Board | Last reviewed: May 2020 | Last updated: March 2021

There are various conditions or diseases that occur at the same time as conditions on the AxSpA spectrum. These are called comorbid conditions. Some of these are more common than others, and early diagnosis of these disorders can help you get prompt treatment and improve symptoms and quality of life. Inflammatory bowel disease (IBD) is one of the more common comorbid conditions. While not curable, it is treatable, so early diagnosis is important.

What is inflammatory bowel disease (IBD)?

IBD is an umbrella term for two conditions: Crohn’s disease and ulcerative colitis (UC). The hallmark of both of these conditions is chronic inflammation of the gastrointestinal (GI) tract.1 When the inflammation is long-term, damage occurs.

Although both Crohn’s disease and UC are both considered IBD, there are differences between the two conditions. Crohn’s disease can affect any part of the GI tract. This means any area from the mouth to the anus can be affected. Typically, it affects the area of the small intestine right before the colon.1 UC affects the colon and rectum.1

Symptoms of IBD can include:1

  1. Diarrhea
  2. Stomach pain
  3. Rectal bleeding/bloody stool
  4. Weight loss
  5. Fatigue

In 2015, approximately 1.3 percent of all adults in the US were living with IBD.2 This is approximately 3 million people.2 People living with conditions on the AxSpA spectrum often have comorbid conditions, including IBD. For people with ankylosing spondylitis (AS, which can also be called radiographic AxSpA or r-AxSpA), the prevalence of IBD can range from 6 to 14 percent.3 It is also estimated that about 60 percent of people with AS have “silent” microscopic gut inflammation. This is gut inflammation that may not have any symptoms or clinical features of IBD.

Silent microscopic gut inflammation can develop into IBD, so it’s important to note any changes in your bowel habits or any associated symptoms and discuss with your physicians. If you do have any unusual bowel symptoms you may be referred to a gastroenterologist, who is a specialist of the GI tract, for evaluation to see if further testing needs to be done.

Why IBD occurs

The exact cause of IBD is unknown, but IBD is caused by an immune system that does not work properly.1 In IBD, the immune system has an improper response to triggers, and this causes the inflammation of the GI tract. There is also a genetic component for many people, since there is often a family history of the condition in those with IBD.1

For those with a diagnosis on the AxSpA spectrum, certain human leukocyte antigen (HLA) alleles have been found in people with IBD who have a higher risk of developing an AxSpA spectrum condition.3 Approximately 25 to 78 percent of people who have AS and IBD are also positive for HLA class I molecule B27 (HLA-B27).3 There are also other genes that have been associated with the conditions as well.

More research needs to be done to see how these genetic components fit together, and what this can mean for treatment options.

How is IBD diagnosed and treated?

IBD is diagnosed through multiple tests, including endoscopy or colonoscopy, and imaging studies like MRI or CT scan.1 Sometimes stool samples or blood tests may also be used to rule out things like an infection and confirm a diagnosis.1

Typically, IBD is treated with medications. Several types can be used: aminosalicylates, corticosteroids, immunomodulators, and biologics.1 If the IBD is severe, surgery might be necessary to remove damaged portions of the GI tract.

For those with a condition on the AxSpA spectrum and IBD, disease modifying antirheumatic drugs (DMARDs) are often used.2 In those for whom DMARDs are not effective, anti-TNF (tumor necrosis factor) drugs are the gold standard.2 These drugs help control inflammation and can treat both AxSpA spectrum conditions and IBD.

Each person with IBD is different, especially if the IBD is comorbid with a condition on the AxSpA spectrum. Treatment regimens can vary depending on the severity of each condition. Talking with your doctor about your symptoms can help you find the right treatment for you that will minimize symptoms.

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