Is Ankylosing Spondylitis Genetic?

Although more research is needed, scientists believe genetics and environmental factors play a role in your risk of developing ankylosing spondylitis (AS). A variation in several genes may increase your risk of AS.

AS can occur in more than one family member. However, it doesn't necessarily mean you will develop the condition, even if you have a genetic variant tied to AS.

Read on to learn more about the genetic factors of AS and how it is diagnosed and treated.

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How Many People Live With AS?

AS affects an estimated one in 1,000 people in the United States.

Inheritance

About 90%–95% of people diagnosed with AS have a gene variant called HLA-B27. There are more than 100 subtypes of this gene, which vary among ethnicities.

However, the overall contribution of HLA-B27 to the heritability of AS is only about 20%, which means many additional genetic factors may contribute to the disease. Other genes that affect how the immune system works, like ERAP1, may also make people more susceptible to developing AS.

How Likely Is AS to Be Inherited?

If you have AS and carry the HLA-B27 gene, there is a 50% chance you will pass this gene down to your child. While not definitively known, it's estimated that 5%–20% of children with that gene eventually develop AS.

Other Causes

Because AS is an autoimmune disease, problems with a person's immune system function may play a role in the development of AS. One study found that compared to a healthy control group, those with AS had different levels of tumor necrosis factor (TNF) and interferon (IFN), two types of proteins that regulate the body's inflammatory response.

Microbial infections may also be a trigger for the development of AS. Certain bacteria found in the gut, including the type causing Klebsiella pneumoniae, could make AS symptoms worse. More research is needed to explore the relationship between the microbiome and AS.

Researchers also are exploring whether sex hormones contribute to the development of AS.

Symptoms

AS is a type of arthritis that mainly causes inflammation in the spine, leading to severe and chronic pain. If it becomes advanced, the inflammation can cause bones in the spine to fuse, reducing your range of motion. AS can affect other areas of the body, including the shoulders, hips, ribs, small joints of the hands and feet, and sometimes even the eyes.

Symptoms can include:

Men are 10 times more likely than women to have AS, and symptoms generally start before middle age.

Diagnosis

To work toward a diagnosis, your healthcare provider will do a physical exam and ask questions about your symptoms and your medical and family history. They will look at your joints, watch how you move and bend, and ask you to breathe deeply to check for stiffness and inflammation.

Your provider may also order imaging and lab tests such as:

  • X-rays to help see joint changes, although the disease can be present for a long time before any such changes can be seen on an X-ray
  • Magnetic resonance imaging (MRI) to see the joints better
  • A blood test to check for the HLA-B27 gene

Treatment

There is no cure for ankylosing spondylitis, but it can be treated. The goals of AS treatment include:

  • Maintaining spinal flexibility and normal posture
  • Alleviating pain and stiffness
  • Reducing the risk of joint damage
  • Slowing the progression of the disease

Medications used to treat AS include:

Physical therapy may help strengthen muscles, improve posture, ease pain, and maintain flexibility.

Surgery may be recommended if joint damage is severe and everyday activities are nearly impossible. This is not for everyone, and you and your provider will need to discuss your options to decide what's best for you.

Prognosis

The severity of AS symptoms and the way the disease progresses can vary among individuals. Many people with AS will have acute and painful episodes (flares) followed by temporary periods of being symptom-free or having reduced symptoms. In some cases, people may be disabled from the effects of AS. Early diagnosis and treatment may decrease the chances of joint damage.

AS is a chronic, lifelong disease. It cannot be cured, but it can be treated and managed. It’s important to see your treatment team regularly, even if your symptoms are under control. There may be complications you’re not aware of, and it’s always a good idea to monitor the progression of your AS and address any issues as early as possible.

Summary

AS is a chronic condition that can be painful and even debilitating. Accurate diagnosis is important so that it can be appropriately treated and managed. There is a strong genetic component to AS, although it is not the only potential cause.

Other possible causes include microbial, immunological, and hormonal factors. While AS cannot be cured, treatments like medications, physical therapy, and surgery, if warranted, can help ease symptoms and improve mobility.

Frequently Asked Questions

  • Can ankylosing spondylitis be inherited?

    Yes. There is a genetic component to AS, but it is not the only potential cause of AS. Multiple factors may be involved, and a definitive, single cause is not known at this time.

  • Is the ankylosing spondylitis trait dominant or recessive?

    AS does not follow a clear pattern of being a recessive or dominant trait. It is known as oligogenic with multiplicative effects, which means that several gene variants influence inheritance, and the more of those variants present, the greater the risk.

  • How is ankylosing spondylitis diagnosed?

    Ankylosing spondylitis is diagnosed with a medical and family history, physical exam, imaging tests, and possibly blood tests. It is important for your healthcare provider to get a well-rounded picture and as much information as possible before making a definitive diagnosis.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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