Ankylosing = stiffening or joining together
Spondylitis = inflammation of the vertebrae
Ankylosing spondylitis (AS) affects between 1 in 100 and 1 in 200 people and is a form of arthritis that mainly affects the spine. It usually begins between the ages of 15 and 40 years although diagnosis is commonly delayed for five to seven years.
About 50% of AS sufferers develop arthritis of limb joints such as the shoulders, hips and knees. Inflammation at sites where tendons insert into bone (called enthesitis) frequently occurs. Chest wall and rib cage pain is common. Less commonly, inflammation can occur in other areas such as the eye (uveitis), bowel (colitis), lung (fibrosis) and heart (aortitis).
People with AS commonly complain of pain, stiffness and fatigue. In more severe cases, there is loss of mobility, ability to work and general independence. Approximately 70% will develop some fusion of the spine after 10-15 years.
HLA-B27 is a normal genetic variant and occurs in approximately 8% of Caucasians. Of these, only about 12% will develop AS or a similar condition. However, approximately 90% of people with AS are HLA-B27 positive. Clearly, the gene alone does not cause AS. It is likely that AS is brought on by an unknown trigger in a genetically predisposed individual.
A first degree relative (child, sibling or parent) who is HLA-B27 positive has about a 30% chance of developing AS. An identical twin of someone with AS has a 60% risk while the risk for a non-identical twin is 20%.
The activity of AS is judged by severity of symptoms especially fatigue, stiffness in the spine and morning stiffness. At any given time, approximately 30% of individuals with AS have active disease.
The long term course in AS usually parallels the severity of symptoms over the first 10 years of symptoms. Recognised predictors of more severe features of AS include early age at onset, hip involvement, eye inflammation and smoking.
The most important treatments for AS are daily exercise and anti-inflammatory medications (e.g. Indocid, Naprosyn, Voltaren, Neurofen, Feldene). For many patients with AS, TNF (tumour necrosis factor) blockers can dramatically improve symptoms, spinal mobility and day-to-day functioning.
A daily exercise program is critical for maintaining good posture, spinal mobility and daily functioning. If possible, the exercise program should be reviewed by an expert physiotherapist.
Anti-inflammatory medications work reasonably well in controlling pain and stiffness. Some patients can develop intolerable side effects.
Many individuals with AS are treated with these medications although they work less well than in rheumatoid arthritis. Clinical trials have shown only sulfasalazine to be helpful and only for arthritis of the limbs.
TNF stands for tumour necrosis factor which is a molecule that promotes many of the clinical features of AS. These treatments inhibit the effects of this molecule. Currently, there are three TNF-blockers available for active AS: infliximab (Remicade®), etanercept (Enbrel®) and adalimumab (Humira®).
Remicade is administered via an intravenous (into the vein) infusion in a day treatment centre. Enbrel and Humira are given by a self-administered subcutaneous (under the skin) injection.
Recognised risks include infection (particularly tuberculosis in those previously exposed to tuberculosis), low blood counts, liver function test abnormalities, heart failure, autoimmune conditions, multiple sclerosis and possibly certain cancers. You will need to discuss these with your rheumatologist before considering these treatments.
After a three-month course of exercise and at least two anti-inflammatory medications, one needs to demonstrate symptoms of active disease, decreased spinal mobility, x-ray abnormalities at the sacroiliac joints and an elevated ESR and/or CRP. Your rheumatologist would be happy to discuss these criteria with you.