What is ankylosing spondylitis?

Ankylosing spondylitis (AS) is a type of arthritis. It causes inflammation of the joints of your spine, resulting in pain. AS often affects the sacroiliac, the joint where the base of your spine and your pelvis meet.

No one knows what causes AS, but genetics are involved. People inherit genes that make them more likely to get this condition. Then an unknown trigger, possibly an infection, starts the disease process.

About 2.7 million American adults have AS or other type of spondylitis, according to the Spondylitis Association of America.

AS is most common in young men: The condition usually starts between ages 17 and 45. However, women and children can also get AS. People who have the HLA-B27 gene and a family history of the disease are more likely to get AS. However, you don’t need the gene to have AS, and some people who do have it never get the disease.

The most common symptom of AS is sacroiliitis. The sacroiliac joints are located at your spine’s base, where it connects to your pelvis. When they become inflamed, they cause pain in your lower back and buttocks. This can even cause pain in your legs. The pain can worsen if you stand for a long period of time. If your doctor suspects AS, they will likely check for sacroiliitis.

When AS is severe, the vertebrae of your spine can grow together and fuse. The fused bones may force your spine into a forward curve. This is called kyphosis. As your spine curves, your back curls into a stooped-over position. People with severe AS may be so bent over that they have trouble even lifting their head. Treatment advances have made kyphosis less common.

AS affects your spine, but it can also cause pain and stiffness in other parts of your body including your hips, lower back, neck, and shoulders. Pain and other symptoms of AS start slowly. In fact, you may not notice them at first. But they can get worse over time, and the pain may come and go. Or you may be in constant pain. Some people notice stiffness more in the morning when they wake up.

AS may also be accompanied by osteoporosis, even in the early stages of the disease. Over time, your bones can become brittle and are more likely to fracture. If the fractures are in your spine, the vertebrae may collapse and cause your back to bend forward even more than it already does. Some fractures can even compress nerves in your spine.

One of the most common features of AS involves inflammation of your eyes. This inflammatory eye condition is called uveitis. Your eyes can swell up, causing pain, blurred vision, and sensitivity to bright light. They may also get very red and watery. Uveitis is a serious complication of AS. Call your doctor for an appointment right away if your eyes start to bother you.

When you breathe, your lungs expand. The rib cage that houses and protects your lungs also expands slightly. If the joints of your ribs are inflamed from AS, their movement may be restricted. You may feel pain when you breathe. And you probably won’t be able to inflate your lungs all the way. This will make it hard for you to catch your breath.

Fatigue is one of the biggest complaints people with AS have, according to the Spondylitis Association of America. It takes a lot of energy for your body to deal with the inflammation AS causes in your body. Also, the pain of AS can make it hard for you to sleep. Some people with AS have anemia—too few of the blood cells that transport oxygen to the body. All of these things may make you feel more tired than usual.

Because AS is a type of arthritis, you’ll see a doctor called a rheumatologist to treat it. To find out whether you have AS, you’ll have an exam. The doctor will ask about your symptoms and check your back. You may also have tests, including X-rays or MRI scans to look at your spine from the inside. A blood test can find out whether you have the HLA-B27 gene.

There is no cure for AS, but treatments can reduce pain and help you feel better. You can take medications such as NSAIDs for this purpose. There are also medications called disease-modifying antirheumatic drugs, or DMARDs, that slow the disease and reduce swelling in the joints of your spine. Stretching and exercising can help with stiff joints and improve your movement. Sometimes a damaged joint may need to be replaced through surgery.