Ankylosing spondylitis (AS) is also known as Bechterew's disease; Bechterew syndrome; Marie Strümpell disease / Marie Struempell disease / Spondyloarthritis).
AS is a chronic, painful, progressive rheumatic disease that causes chronic inflammatory arthritis of the spine and sacroiliac (SI) joints--resulting in eventual fusion--and can cause inflammation of the eyes, lungs, and heart valves. The person exhibits intermittent episodes of back pain that occur throughout life. AS does not necessarily starts bilaterally. Research clearly indicates that the iliac, not the sacral side and the dorsocaudal part of the SI joints are affected early on. Complete fusion results in a complete rigidity of the spine, a condition known as bamboo spine
TESTS:
Tests may include:
- HLA-B27 antigen test is positive.
- A spine X-ray or pelvis X-ray shows characteristic findings. Routine lumbar spine and sacroiliac joint X-rays are only recommended for HLAB27-positive patients.
- ESR may or may not be elevated. Elevation may be mild.
- CBC may show mild anemia.
- Magnetic resonance imaging has proved useful for visualising inflammation in the SI joints in adults and children.
GENETICS:
Ankylosing spondylitis is relatively rare. It is considered a multifactorial disorder, or one that is the result of both genetic and environmental factors interacting. Two genes have been identified that confer susceptibility to AS, both of which are forms of an HLA gene on chromosome 6 (detected by a blood test).
Some HLA types have been implicated in various autoimmune diseases, meaning diseases in which the immune system attacks the body's own cells and tissues. Researchers have determined, however, that a particular version of the HLA-B gene (called HLA-B27) increases the risk of developing this disorder. The association of HLA B-27 and AS has been clearly established. Ninety-five percent of individuals with AS are B-27 positive, and since AS appears to be a dominant trait, the presence of at least one B-27 allele (a form of the gene) confers a greatly increased chance of developing symptoms. While this population risk may seem relatively high, it is important to realize that only about 9% of the population carries the B-27 allele. Of these individuals who are B-27 positive, only 2–8% will develop AS. It is not known how HLA-B27 increases the risk of developing ankylosing spondylitis. HLA-B27 is a Class 1 HLA molecule found in 95 per cent of patients with AS, compared with a prevalence of 9 per cent in the normal population in the UK.
What is clear, is that the prevalence of AS parallels that of HLA-B27 and AS occurs with a greater prevalence in ethnic groups with a high population prevalence of B27, for example, the Haida Indians of North America.
The pathogenetic role of B27 in AS is uncertain, but it may be associated with a number of genes that confer susceptibility to the disease. The HLA-B gene provides instructions for making a protein that plays an important role in the immune system. HLA-B is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). The HLA-B gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign invaders. Other genes are believed to affect the chances of developing ankylosing spondylitis and influence the progression of the disorder. Some of these genes likely play a role in the immune system, while others may have different functions. Researchers are working to identify these genes and clarify their role in ankylosing spondylitis.
The cause of AS is not known and there is no cure. Delayed diagnosis is common because symptoms are often attributed to more common back problems.
Ankylosing spondylitis is 2-3 times more common in males than in females, which is why I was stunned when I was diagnosed with AS in 2001.
Other environmental and genetic factors most certainly contribute to development of the disease. This becomes more evident when considering that B-27 positive individuals with an affected first-degree relative have a significantly higher chance of developing AS than a B-27 positive individual with no family history. In families with multiple affected members, studies estimate that no more than half of AS recurrence is explained by HLA type. Additionally, there are several B-27 subtypes that have been studied; some confer susceptibility and some do not. Importantly, about 5% of people with AS are B-27 negative. Other environmental and/or genetic factors must certainly be associated with disease in these individuals. Another HLA type—B-60—has also been shown to confer susceptibility, although the association appears to be much weaker and is not seen in all studies. Certain infections are suspected as being necessary for triggering AS in some individuals. In the future, additional susceptibility genes and environmental factors can be expected to be identified.
DEMOGRAPHICS
Ankylosing spondylitis affects about 0.5 percent of people of Western European descent. In the US: AS affects 0.1-0.2% of the US population. Internationally: AS affects 0.1-1.0% of the world population. Native North Americans, Alaskan Eskimos, and Norwegian Lapps all have relatively high levels of B-27 and AS. Low levels of B-27 and AS occur among individuals of most types of African ancestry, Australian aborigenes, and Native South Americans.
SIGNS AND SYMPTOMS
SIGNS AND SYMPTOMS
The signs of AS vary, but a typical case involves slow or progressive onset of lower back pain and stiffness (typically in the morning) over weeks or months, rather than hours or days. Other symptoms include fatigue, feeling feverish and experiencing night sweats, early onset weight loss, and feeling better after exercise and worse after rest. The earliest symptoms of this disorder result from inflammation of the joints between the base of the spine (the sacrum) and the hipbones (the ilia). These joints are called sacroiliac joints, and inflammation in this region is known as sacroiliitis. The disorder also causes inflammation of the joints between vertebrae, which is called spondylitis.
Ankylosing spondylitis can involve other peripheral joints and other body organs as well, including the shoulders, hips, and, less often, joints in the limbs, resulting in severe joint and back stiffness, loss of motion and deformity as life progresses. Over time, this disorder can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe. Breathing exercises can help to maintain lung capacity. Crohn's disease and ulcerative colitis are found in 10-15% of patients with AS.
Ankylosing spondylitis can involve other peripheral joints and other body organs as well, including the shoulders, hips, and, less often, joints in the limbs, resulting in severe joint and back stiffness, loss of motion and deformity as life progresses. Over time, this disorder can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe. Breathing exercises can help to maintain lung capacity. Crohn's disease and ulcerative colitis are found in 10-15% of patients with AS.
- heart valve disease, typically aortic valve stenosis
- aortitis
- eye inflammation (uveitis/iritis)
- pulmonary fibrosis
- kidney failure (rare complication)
- osteoporosis can cause spinal fractures
- Ankylosing spondylitis usually starts with dull pain in the low back and back stiffness. Some people with ankylosing spondylitis have "flares" of increased pain and stiffness that may last for several weeks before decreasing again.
- Affected bones of the low back, middle back, hips, or neck may become painful, stiff, and limited in motion. Pain tends to increase slowly over a period of weeks or months, and it is often hard to point to exactly where the pain is. Stiffness is usually worse in the morning. Physical activity often helps decrease pain and stiffness.
- A feeling of tiredness is common as the disease progresses. This tiredness comes from the body fighting the inflammatory process that is part of ankylosing spondylitis, and from ongoing stiffness and pain.
- The colored part of the eye (iris) may become inflamed. This inflammation, called iritis, occurs in about 25% to 30% of people with ankylosing spondylitis. Symptoms of iritis include redness and pain in the eye and sensitivity to light.
Severe or advanced ankylosing spondylitis
If, over time, the inflammation continues, it will lead to scarring and permanent damage.
- Scarring in the spine causes the joints of the spine to grow together (fuse, or "ankylose"). As the bones fuse, back pain will gradually go away, but the spine will remain very stiff and unable to bend. The fused spine is more likely to fracture if injured, especially the neck (cervical spine).
- Changes in the spine can cause problems with balance, safety, and mobility. The upper spine can curve forward until eventually the person has a hard time looking straight ahead. In addition, as the spine loses its natural curves it becomes hard to balance for standing and walking, especially if the hips are also affected.
- Breathing can become difficult as the upper body curves forward and the chest wall stiffens. Severe ankylosing spondylitis can also cause scarring of the lungs (pulmonary fibrosis) and an increased risk of lung infection. This can cause even greater problems in smokers because their lungs are already more prone to lung infection and scarring.
- Scarring in the eye can lead to permanent visual impairment and glaucoma.
- In rare cases, the heart muscle can become scarred and the heart valves may become inflamed. The heart may be unable to pump properly (heart failure). The main artery leading from the heart (aorta) can also be affected by becoming inflamed and enlarged near where it leaves the heart.
TREATMENT:
The optimal treatment of ankylosing spondylitis involves medications that reduce inflammation or suppress immunity, physical therapy and exercise to maintain mobility and flexibility.
MEDICATIONS:Nonsteroidal anti-inflammatory medications (NSAIDs) such as aspirin and indomethacin are used to reduce inflammation and pain associated with the condition. They allow patients to exercise, which improves posture and breathing.
Corticosteroid therapy or medications to suppress the immune system may be prescribed to control various symptoms. Some health care professionals use cytotoxic drugs (drugs that block cell growth) in people who do not respond well to corticosteroids or who are dependent on high doses of corticosteroids.
TNF-inhibitors, such as Enbrel, have been shown to improve the symptoms of ankylosing spondylitis.
SURGERYSurgery is done if pain or joint damage is severe.
LIFESTYLE CHANGESExercises can help improve posture and breathing. Lying flat on the back at night can help maintain normal posture. Use devices to help with activities of daily living.
PROGNOSIS:
The course of the disease is unpredictable. The disease activity in AS usually fluctuates; remissions and relapses may occur at any stage. The majority of patients with mild disease are able to maintain a reasonable functional and employment capacity unless the hips are severely involved, but a significant minority of patients with severe disease develop progressive functional impairment. One study identified seven variables that correlated with disease severity and hence poorer prognosis:
* Hip arthritis
* Dactylitis (a sausage-shaped swelling of the fingers and toes which can be painful)
* Poor NSAID response
* High ESR (>30mm/h)
* Reduced range of lumbar spine movement
* Peripheral joint disease
* Disease onset age
Only 1 per cent of patients enter long-term remission. Prognosis is adversely affected by smoking, recurrent extra-articular complications and peripheral joint disease. Recent research suggests that AS patients are also at increased risk of cardiovascular complications because of their chronic, low-grade spinal inflammation.
References:
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McLauchlan GJ, Gardner DL. Sacral and iliac articular cartilage thickness and cellularity: relationship to subchondral bone end-plate thickness and cancellous bone density. Rheumatology (Oxford) 2002;41:375–80.
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