Dr Chris Steele provides information about Ankylosing Spondylitis, a painful and progressive rheumatic disease.

Ankylosing Spondylitis (AS)

Ankylosing Spondylitis (AS) is a painful and progressive rheumatic disease that causes some, or all of the sacroiliac joints in the spine to fuse together. In addition to the spine, about 20% of individuals have significant involvement of peripheral joints, including the hips, knees and shoulders. AS can also affect other parts of the body, including the eyes, lungs, bowel and heart.

Symptoms

Early signs include low backache and stiffness, particularly during the early morning, but these are frequently misdiagnosed as common back pain. Other typical features of AS include: persistence for more than three months; improvement following exercise, and exacerbation after rest; weight loss, particularly during the early stages; fatigue; and fever and night sweats.

40% of people with AS will develop iritis or uveitis (inflammation of the iris). AS can also have a mild impact on the heart and can affect the rib joints and muscles, making breathing, sneezing, coughing or yawning painful.The severity of AS varies: some people have virtually no symptoms while others suffer more severely.

AS is an auto-immune disease, a condition in which the immune system attacks the body’s own healthy tissues. Other examples of auto-immune diseases include rheumatoid arthritis, psoriasis, psoriatic arthritis, rheumatoid arthritis, ulcerative colitis and Crohn’s disease.

Causes

The cause of AS is not known. About 90% of people with AS share the same genetic cell marker HLA-B27. It is possible that a normally harmless external factor such as a micro-organism reacts with the gene marker and triggers the condition. Sometimes a bowel infection appears to spark off AS. If a parent has AS there is a 50% chance that the B27 gene will be passed on to a child. However, this does not mean they will go on to develop AS.

How common is AS?

AS affects approximately 1 in 200 men and 1 in 500 women in Britain. It typically strikes people in their late teens and twenties, with the average age being 24. Approximately three times as many men as women are affected by AS. It tends to affect males and females in slightly different ways: in men, the pelvis and spine are most commonly affected whilst in women, the joints most frequently affected are the pelvis, hips, knees, wrists and ankles. In youngsters, AS tends to affect the knees, ankles, feet, and hips. It may lead to persistent hip disease, requiring a hip replacement in later life.

Diagnosis

Diagnosing AS can be difficult since it is often mistaken for common back pain and there is typically a 10-year delay before the condition is diagnosed. Specific blood tests sometimes show an abnormal result in the early stages. These include erythrocyte sedimentation rate (ESR), plasma viscosity or C-reactive protein tests. Early diagnosis can be significantly enhanced by using MRI scans of the spine and sacroiliac joints. These can detect very early changes due to inflammation, whereas X-rays may only be able to identify changes which have developed over months or years months. As 90-95% of patients with AS carry the HLA-B27 gene, genetic testing for this can be useful, although it cannot provide a definitive diagnosis, as not everyone goes on to develop the disease.

Treatment

There is no cure for AS. The goals of treatment are to relieve symptoms, improve spinal mobility and allow the patient to maintain a normal life as far as possible.

Treatment options include analgesics and non-steroidal anti-inflammatory drugs (NSAIDS), disease-modifying drugs and anti-TNF therapy. It is also vital to pay attention to good posture, mobility and to take appropriate exercise.

Analgesics and NSAIDs can be effective at controlling the pain and stiffness of AS.

Disease-modifying drugs, such as sulfasalazine and methotrexate, attack the causes of inflammation in the joints, but take take weeks or even months to become effective. They are more likely to benefit the arthritis in the limb joints rather than in the spine.

More recently, anti-TNF therapy has been licensed for the treatment of AS that specifically target TNF-alpha, a product of the body's own immune system which plays an essential role in inflammation. TNF inhibitors are different from other medications for AS, as they are designed to block specific molecular steps in the pathogenesis of the disease.

Three treatments are currently licensed in the UK for the treatment of patients with severe AS who have responded inadequately to conventional therapy. Etanercept (Enbrel) and adalimumab (Humira) are given as twice-weekly self-administered subcutaneous injections. Infliximab (Remicade) is administered intravenously as hospital or day care treatment every eight weeks following an induction regime.


This content was created on Thu 12 April 2007

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