The Facts

Ankylosing spondylitis (AS) is a type of arthritis that causes inflammation inthe joints of the spine. The most common areas affected are the sacroiliac joints, which are the joints at the base of the spine that connect the spine and the pelvis. Other joints, such as the hips and shoulders, may also be similarly affected. AS causes pain, stiffness, and inflammation at the affected joints.

About 1% of Canadians have AS. Having a family member with AS increases your risk of developing the condition, since the disease is at least partly hereditary. People with a certain molecule called HLA B27 on the surface of their cells are also more likely to get AS. Having both HLA B27 and a family history further increases your risk: about 1 in 5 of these people will develop AS. If you carry this molecule, however, without a family history, the chance of getting this condition is less than 1 in 10.

AS affects about three times as many men as women. People with AS tend to be of medium height with a slim build and a long, narrow face. Most people are first diagnosed between the ages of 15 and 40 years. However, younger and older people can also be affected.

Causes

The cause of AS is not completely understood, but it's believed to be at least partly related to genetics. AS is more common in people with a family history of the condition. Scientists believe that AS is "triggered" by something in the environment, such as an infection, for people whose genes put them at risk of AS. The immune system responds to this trigger by producing chemicals that cause inflammation in the spine and other joints of the body. There is no evidence, however, that an infection causes the disease.

It is also known that people with a molecule called HLA B27 on the surface of their cells are at higher risk of developing AS. HLA B27 can be passed down from parent to child. Although it increases the risk of AS, not everyone with HLA B27 will get AS.

Symptoms and Complications

AS can cause a variety of different symptoms, but most people with AS have low back pain and stiffness. The stiffness is often worst in the morning and after you have been inactive for a while. The back pain and stiffness can prevent you from moving around comfortably and getting a good night's sleep.

Other joints can also become affected by AS, such as the hips, shoulders, and knees. People with AS can experience fatigue, weight loss, and loss of appetite. The symptoms of AS tend to come and go, with periods of no symptoms followed by flare-ups.

AS can cause complications both in the joints and elsewhere in the body, including:

• bent-over or unusually straight posture
• limited mobility (ability to move around)
• eye inflammation (which can cause eye pain, irritation, and sensitivity to light)
• breathing problems due to stiffness in the joints between the spine and the ribs
• inflammation in places where ligaments and tendons attach to the bone (called enthesitis)

Very rare complications can include:

• inflammation of the aorta, a large blood vessel that brings blood from the heart to the rest of the body
• heart valve damage
• spinal cord injury due to fractures (breaks) in the spine
• cauda equina syndrome, where AS damages the nerves at the base of the spinal cord, leading to loss of sensation in the buttocks, rectum, thighs, and bladder; or loss of bowel or bladder control

Making the Diagnosis

Your doctor will make the diagnosis of AS based on your symptoms and an X-ray or another type of imaging of your affected joints. If you have AS, the X-ray will show areas where the bone has been worn away by the condition. The vertebrae of the spine may start to fuse together because the ligaments between them become calcified. The term for bones growing together due to inflammation is ankylosis, and this is where the name ankylosing spondylitis comes from. ("Spondyl" refers to the spine and "itis" means inflammation.)

Your doctor may also do a blood test called erythrocyte sedimentation rate, or ESR for short, or a C-reactive protein test (CRP). A high ESR or CRP is a sign of conditions with inflammation, such as AS. However, it does not definitely mean that you have AS, since many other conditions can also cause a high ESR or CRP.

Treatment and Prevention

Currently, there is no cure for AS. But it can be managed using medications, surgery, and physiotherapy.

Medications:
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin*, diclofenac, ibuprofen, naproxen, and others work by reducing inflammation, which helps relieve the pain, stiffness, and swelling of AS. They do not slow down the progression of the condition. In other words, they don't stop the disease from getting worse. Possible side effects of NSAIDs include nausea, abdominal pain, stomach ulcers, and bleeding.

Corticosteroids, such as prednisone, triamcinolone, and methylprednisolone, work by reducing inflammation. They are used to relieve symptoms. Corticosteroids do not slow down the progression of the condition. They may be injected into an affected joint or taken by mouth. Side effects of the injection include joint damage (if the injection is used too often). Short-term side effects of the pills include increased appetite, weight gain, menstrual changes, and stomach irritation. Long-term use of high doses can lead to diabetes, cataracts, glaucoma, increased risk of infection, high blood pressure, osteoporosis (bone thinning), moon face (rounding of the face), mood changes, acne, or increased body hair.

Biologics, such as adalimumab, etanercept, and infliximab, are used to relieve signs and symptoms of the condition, including symptoms in the spine. Some biologics can also help to improve physical function for people with AS. They work by neutralizing a molecule called tumour necrosis factor alpha (TNF-α). TNF-α, which is involved in causing inflammation. Depending on the medication, biologics are given as an injection under the skin (a subcutaneous injection) or as an injection into the vein over a period of time (an intravenous infusion). Possible side effects include infusion reactions (such as rash, flushing, headache, and difficulty breathing), irritation at the injection area, nausea, headache, vomiting, diarrhea, fatigue, joint pain, or an increased risk of infection.

Disease modifying antirheumatoid drugs (DMARDs), such as methotrexate, are used to relieve AS symptoms and slow down the progression of the condition. They do not relieve inflammation in the spine. Possible side effects include nausea, diarrhea, increased risk of infections, liver damage, and bleeding.

Surgery:
Surgery may be used to repair joint damage or replace damaged areas. For example, some people with AS may need a hip replacement.

Physiotherapy:
A physiotherapist can show you special exercises to improve your flexibility, strength, and mobility.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For more information on brand names, speak with your doctor or pharmacist.