Ankylosing spondylitis: Causes, symptoms, diagnosis and treatment

What is ankylosing spondylitis?

Ankylosing spondylitis is a form of arthritis that mainly targets the spine. Over time ankylosing spondylitis can cause your spine to become stiffer, and eventually the vertebrae (bones in your spine) may fuse together. People have a tendency to develop a stooped-over posture as the disease progresses. It affects around 120,000 people in the UK.

You may also experience other complications including arthritis of the hip joints and the joints between the ribs and the breastbone, between the ribs and the spine, bone spurs and inflammation in the feet, inflammation of the eyes and scarring of the lungs. Severe disease may lead to poor posture and deformities.

Ankylosing spondylitis is around three times more common in men than in women. Most symptoms of ankylosing spondylitis start in early adulthood, before reaching 40 years old, although some may have symptoms in early adolescence or, occasionally, even in childhood.

What causes ankylosing spondylitis?

The cause of ankylosing spondylitis is unknown, although researchers have shown that people with this disorder are more likely to have a certain genetic marker called HLA-B27. If there is a family history of ankylosing spondylitis in parents or siblings and a person is also positive for the HLA-B27 marker, there is a 20% chance for that individual to develop ankylosing spondylitis if he or she is less than 40 years old. The odds are much lower in those greater than 40 years old. Also, some researchers are exploring an association between certain bacteria and ankylosing spondylitis.

What are the symptoms of ankylosing spondylitis?

It's important to note that not everyone develops all of the following symptoms, but that these are possibilities depending on the severity of the condition.

• Stiffness and pain in the lower back, buttocks and hips upon waking in the morning or after a period of inactivity
• Back pain relieved by movement and exercise
• Difficulty bending the spine
• Pain in the hips and difficulty walking
• Pain in the heels and soles of the feet
• Bent-over posture
• Straightening of the normal curvature of the spine
• Fever
• Loss of appetite, weight loss
• Fatigue, decreased energy
• Eye swelling, redness and pain
• Sensitivity to light
• Difficulty taking a deep breath (because expanding the chest is difficult and painful)
• Heart failure

Seek medical advice if:

• You develop persistent lower-back pain.
• You notice that your back feels painful and stiff in the morning but improves with movement and exercise.
• You have any difficulty or pain drawing a deep breath.
• You have redness or swelling in an eye, or you are abnormally sensitive to light.
• You develop unexplained fever, loss of appetite, weight loss or fatigue.

How do I know if I have ankylosing spondylitis?

There is no definitive test to diagnose ankylosing spondylitis. Most doctors expect to see X-ray evidence of inflammation of the joint between the sacrum (the triangular bone at the lowest part of the back) and the ilium (the bone felt on the upper part of the hip), as well as any one of the following signs:

• Inflammatory back pain (gradual in onset, lasting over three months, with stiffness and pain that is worse in the morning and improved with movement).
• Reduced mobility of the spine.
• Reduced ability to expand the chest.

Your doctor may arrange a number of different blood tests that can suggest ankylosing spondylitis. For example, if you have ankylosing spondylitis, you are likely to have an increased erythrocyte sedimentation rate (the rate at which red blood cells settle out of your blood) and increased levels of C-reactive protein (a protein that is usually not in blood but may be in cases of inflammation). These two tests are general indications of inflammation in your body. You may have anaemia and your blood will probably not show rheumatoid factor (an antibody common in cases of rheumatoid arthritis) or anti-nuclear antibodies (common in cases of lupus and other similar conditions). Approximately 95% of people with ankylosing spondylitis are positive for the HLA-B27 marker.