What Is Ankylosing Spondylitis?

Ankylosing spondylitis is also known as Marie-Strumpell disease or Bechterew’s disease. It’s a form of inflammatory arthritis that primarily affects your spine. After several years, the bones in the spine, called vertebrae, may fuse together. When this happens, the spine becomes stiff and less flexible.

Ankylosis: joints fuse together and become unmovable

Spondylitis: inflammation involving the spine’s vertebrae and facet joints

AS often develops in the sacroiliac joints (SI joints), which connect your lower spine to your pelvic bones. It can also develop in other parts of your spine and cause symptoms and conditions elsewhere in your body.

Sometimes, AS can affect your posture. For example, you may develop a hunched back. Doctors call this kyphosis, an abnormal forward position of the upper spine

What Are Possible Ankylosing Spondylitis Causes?

Inflammation is your immune system’s way of fighting illness and injury. During an inflammatory response, chemicals and cells in your bloodstream rush to protect healthy tissue and repair any damage done. This can cause pain and swelling, among other symptoms. When you have AS, the inflammatory response doesn’t work like it should. Instead, inflammation is triggered in healthy parts of your body—including your spine and SI joints.

Gender. Experts used to believe men were up to nine times more likely to have AS than women. But in recent years, research has shown the difference is much smaller than we thought—if there is one at all. One possible reason: Women may have been misdiagnosed or underdiagnosed in the past.

Family history. If your parents or grandparents have AS, you’re more likely to develop it yourself.

HLA-B27: Human leukocyte antigen B27 (HLA-B27) is a protein you may have in your blood. It’s found in the vast majority of Caucasian people with AS, and about half of Black people with AS.

Having the HLA-B27 protein doesn’t mean you have AS—and vice versa. You can have AS without this marker, and you can have this marker without developing AS.

What Are Ankylosing Spondylitis Symptoms?

Symptoms of AS can start at any age, but they often begin before 45. They may differ greatly from one person to another, though some are very common—including those on this ankylosing spondylitis symptoms checklist:

Chronic pain and stiffness. These symptoms typically occur in the lower back first, and frequently the hips and buttocks, too. The discomfort usually builds up slowly, over a period of weeks or months. It can be located on one side of the body, both sides, or go back and forth between sides.

Some people experience intermittent back pain, and others have serious pain and stiffness for long periods of time. Almost all cases of AS are characterized by acute pain followed by temporary remission when symptoms subside.

Discomfort at certain times of the day. Many people with AS feel sore and stiff first thing in the morning, as well.

Inflammation in key areas. If you experience discomfort in different parts of your body, AS could be to blame. The places most often affected by AS include:

• SI joints
• Lower back vertebrae
• Hip and shoulder joints
• The entheses, or areas where tendons and ligaments attach to bones, mainly in your spine but sometimes at the back of your heels
• Cartilage around your ribs and breastbone

How Can You Get an Ankylosing Spondylitis Diagnosis?

Since symptoms often come on slowly and can resemble those of other conditions, it frequently takes years for AS to be correctly diagnosed. But a diagnosis is critical to getting the right treatment early on. If you believe you might have AS, your best bet is to see a doctor called a rheumatologist, who specializes in musculoskeletal and some autoimmune diseases.

Instead, your rheumatologist will use a combination of methods to pinpoint AS and rule out other conditions, called a differential diagnosis. These methods may include the following.

Physical exam. To get to the root of your problems, your provider will look for pain, swelling and tenderness at certain points around your body, such as your back, SI joints, pelvis and heels. They’ll also check for mobility limitations in your spine and other joints. This may involve a few simple, in- office tests requiring you to perform certain movements.

During a Schober test, for example, your provider would assess your lower back flexibility by asking you to bend forward. And for a Gaenslen test, you would be asked to lie down and flex one of your knees while your provider applies pressure to your other leg. This helps to evaluate pain in the SI joints.

Medical history. This will entail a rundown of your symptoms, as well as their severity, duration and location. Problems like uveitis and IBD will be considered as well.

Bloodwork. Your doctor will look for the HLA-B27 protein, as well as other markers of inflammation. Evidence of inflammation may hint at AS, but it could also be a number of other conditions.

Imaging. The earliest changes your doctor can spot on an X-ray are likely in the SI joints, though it may be years before there is enough damage to show up. Magnetic resonance imaging (MRI) and computed tomography (CT) are more sensitive tests for AS. These can detect earlier stages of the disease, such as inflammation of the joints before bone changes occur.