Ankylosing spondylitis and ulcerative colitis are distinct conditions that affect different body parts. But having one may cause symptoms that resemble the other and even increase your risk of developing it.

Ankylosing spondylitis (AS) is a type of arthritis that primarily affects your spine. Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) that affects your colon (large intestine) and rectum. But these two conditions may actually be linked.

Scientists aren’t yet clear on what links these two conditions, but they may share similar pathways to development. It’s not uncommon for people to develop both conditions, usually with one developing before the other.

Keep reading to learn more about the link between these two inflammatory conditions, including symptoms to look out for that may indicate you have both and what that may mean for your treatment and outlook.

AS and UC are both inflammatory conditions. While they primarily affect different parts of your body, research suggests they may share similar pathways of inflammation.

This means that developing one condition could cause symptoms that resemble the other. It’s not unusual for people with AS to experience digestive symptoms, nor is back pain with UC uncommon.

It also means that both conditions may develop together. About 5–10% of people with AS also have an IBD, like UC. And according to a 2017 research review, 3% of people with UC develop AS, with several more developing other types of spondyloarthritis.

Role of HLA-B27

This link is even stronger in people who carry the HLA-B27 gene, a gene linked to several inflammatory conditions.

Even though most people with the gene do not go on to develop AS, the incidence of the gene is much higher among people with AS. Still, the link between HLA-B27 and AS is not entirely clear.

Some research suggests that HLA-B27 may also affect your gut microbiome, the microbes that live in your intestines. These can be both helpful and harmful. Upsetting the balance of your gut microbiome can lead to digestive issues.

More than 70% of people with AS experience gut inflammation, but it’s often not significant enough to cause symptoms. When digestive symptoms of AS do occur, they often include diarrhea and abdominal pain.

Early symptoms of ulcerative colitis

While UC symptoms can vary, there are some common ones to look out for, whether you have AS or not. These include:

  • blood or mucus in your stools
  • diarrhea
  • abdominal pain and cramps
  • sudden or constant urges to pass a bowel movement
  • nausea or vomiting
  • fatigue
  • unintentional weight loss
  • fever
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According to the Crohn’s and Colitis Foundation, arthritis (inflammation of the joints) is the most common nondigestive complication of IBD, affecting up to 3 in 10 people. The reasons for this aren’t clear, but shared inflammatory pathways and genetics may be at play.

Early symptoms of ankylosing spondylitis

Anyone may develop AS, but people with a family history of AS have a higher risk. Most people also develop AS during childhood or adolescence and before the age of 45.

Early AS symptoms include recurring lower back pain that can extend to your hips and extremities. Pain, stiffness, and reduced mobility can eventually spread beyond these areas.

In addition to spine and digestive symptoms, AS can cause inflammation in your:

  • other joints
  • eyes (uveitis)
  • brain
  • skin
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Some UC and AS treatments overlap because they are both inflammatory diseases.

But while you can treat with nonsteroidal anti-inflammatory drugs (NSAIDs) for joint pain in AS, you should not use these medications for UC. Common NSAIDs include aspirin and ibuprofen. These can worsen your UC symptoms.

Instead, a doctor may recommend acetaminophen (Tylenol) for mild pain.

Most people receive a diagnosis of either AS or UC first. If you receive a secondary AS or UC diagnosis, a doctor may modify your treatment. Adjustment options may include:

Below is a summary of common treatments for both conditions:

Ankylosing spondylitisUlcerative colitis
JAK inhibitors or DMARDs
physical therapy

Both AS and UC are manageable with early treatment. This may also slow the progression of each condition.

It’s unclear whether having AS or UC first affects your overall outlook. A small 2023 study noted that overall outcomes were similar for people regardless of whether they developed AS or IBD first.

In the same study, researchers noted that adjustments to treatment didn’t significantly affect people’s outcomes with AS but did more often help them achieve IBD remission.

A long-term study published in 2018 concluded that having AS was linked to a more active course of IBD. However, a 2019 study found that having AS did not worsen your outlook with IBD.

Is there a link between ankylosing spondylitis and Crohn’s disease?

People with Crohn’s disease, another type of IBD, may also be at an increased risk for developing AS.

Which comes first: ankylosing spondylitis or ulcerative colitis?

While more research is needed, people seem to most often develop IBD first before developing AS. In a 2019 study:

  • 68% of people first received an IBD diagnosis
  • 15% first received an AS diagnosis
  • 17% received both diagnoses at the same time

How common is ulcerative colitis in people with ankylosing spondylitis?

Experts think that about 5–10% of people with AS will develop IBD, which includes both UC and Crohn’s disease. One 2023 review places the incidence of UC specifically at 1.66%.

How common is ankylosing spondylitis in people with ulcerative colitis?

According to a 2017 review, about 3% of people with IBD develop AS. A small 2023 study found a higher rate (about 10%), but the authors noted this was more common for Crohn’s disease than UC.

This rate seems to be higher in people who carry the HLA-B27 gene.

It’s not uncommon to have both AS and UC. This most often occurs in people with IBD who develop AS, but it can occur in the other order as well, or they can develop together.

Although it’s unclear what links the two conditions, it may be related to shared inflammation pathways and effects of the HLA-B27 gene.

Since AS and UC are chronic inflammatory conditions with an autoimmune factor, it’s worth discussing both with a doctor and being aware of their possible symptoms.