Ankylosing spondylitis (AS) is a type of arthritis that mainly affects the spine. It causes the vertebrae to become inflamed, 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 is an autoimmune disease and can affect other areas of the body as well, 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. The exact cause is unknown, but genetics are thought to play a role.
Read on to find out more about the genetic factors of AS, plus how it is diagnosed and treated.
How Many People Live With Ankylosing Spondylitis?
AS affects an estimated one in 1,000 people in the United States.
Although more research is needed, scientists believe that genetics plays a role in your risk of developing AS. About 90%–95% of people diagnosed with AS have a gene variant known as HLA-B27. There are more than 100 subtypes of this gene, which vary among ethnicities.
That being said, the overall contribution of HLA-B27 to the heritability of AS is only about 20%, which means there are many additional genetic factors that may be contributing to the disease. For example, 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.
Because AS is an autoimmune disease, it’s likely that problems with a person’s immune system function play a role in the development of AS. One study found that, when compared with 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. In fact, 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.
To work toward a diagnosis, your healthcare provider will ask you questions about your symptoms and your medical and family history, and do a physical exam. The physical exam may involve looking at your joints, watching how you move and bend, and asking 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
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.
If joint damage is severe and everyday activities are nearly impossible, surgery may be recommended. This is not for everyone, and you and your provider will need to discuss all of your options to decide what’s best for you.
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.
AS is a chronic condition that can be painful and even debilitating. Accurate diagnosis is important so that it can be properly 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.
A Word From Verywell
Living with a chronic, incurable condition can be difficult. Talk with your healthcare provider about not only your physical symptoms, but also how you’re handling this emotionally. An AS support group, either in person or online, can be helpful in reducing isolation and providing emotional support.
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 what’s known as oligogenic with multiplicative effects, which means that inheritance is influenced by several gene variants, and the more of those variants that are 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.