Ankylosing Spondylitis

Definition

Definition of Ankylosing Spondylitis
Ankylosing spondylitis, previously known as Bekhterev's disease, Bekhterev syndrome, and Marie-Strümpell disease is a chronic inflammatory disease of the axial skeleton with variable involvement of peripheral joints and nonarticular structures. AS is a form of spondyloarthritis, a chronic, inflammatory arthritis and autoimmune disease. It mainly affects joints in the spine and the sacroiliac joint in the pelvis, and can cause eventual fusion of the spine.

Symptoms

Symptoms of Ankylosing Spondylitis
Ankylosing spondylitis is a form of chronic inflammation of the spine and the sacroiliac joints. The sacroiliac joints are located in the low back where the sacrum (the bone directly above the tailbone) meets the iliac bones (bones on either side of the upper buttocks). Chronic inflammation in these areas causes pain and stiffness in and around the spine. Over time, chronic inflammation of the spine (spondylitis) can lead to a complete cementing together (fusion) of the vertebrae, a process referred to as ankylosis. Ankylosis leads to loss of mobility of the spine.

Ankylosing spondylitis is also a systemic disease, meaning it can affect other tissues throughout the body. Accordingly, it can cause inflammation in or injury to other joints away from the spine, as well as to other organs, such as the eyes, heart, lungs, and kidneys. Ankylosing spondylitis shares many features with several other arthritis conditions, such as psoriatic arthritis, reactive arthritis (formerly called Reiter's disease), and arthritis associated with Crohn's disease and ulcerative colitis. Each of these arthritic conditions can cause disease and inflammation in the spine, other joints, eyes, skin, mouth, and various organs. In view of their similarities and tendency to cause inflammation of the spine, these conditions are collectively referred to as "spondyloarthropathies." Ankylosing spondylitis is considered one of the many rheumatic diseases because it can cause symptoms involving muscles and joints.

Causes

Causes of Ankylosing Spondylitis
The tendency to develop ankylosing spondylitis is believed to be genetically inherited, and a majority (nearly 90%) of people with ankylosing spondylitis are born with a gene known as the HLA-B27 gene. Blood tests have been developed to detect the HLA-B27 gene marker and have furthered our understanding of the relationship between HLA-B27 and ankylosing spondylitis. The HLA-B27 gene appears only to increase the tendency of developing ankylosing spondylitis, while some additional factor(s), perhaps environmental, are necessary for the disease to appear or become expressed. For example, while 7% of the United States population has the HLA-B27 gene, only 1% of the population actually has the disease ankylosing spondylitis. In northern Scandinavia (Lapland), 1.8% of the population has ankylosing spondylitis while 24% of the general population has the HLA-B27 gene. Even among HLA-B27-positive individuals, the risk of developing ankylosing spondylitis appears to be further related to heredity. In HLA-B27-positive individuals who have relatives with the disease, the risk of developing ankylosing spondylitis is 12% (six times greater than for those whose relatives do not have ankylosing spondylitis).

Recently, two more genes have been identified that are associated with ankylosing spondylitis. These genes are called ARTS1 and IL23R. These genes seem to play a role in influencing immune function. It is anticipated that by understanding the effects of each of these known genes researchers will make significant progress in discovering a cure for ankylosing spondylitis.

Diagnosis

Diagnosis of Ankylosing Spondylitis
There is no direct test to diagnose AS. A clinical examination, MRI and X-ray studies of the spine, which show characteristic spinal changes and sacroiliitis, and a simple genetic marker blood test are the major diagnostic tools. A drawback of X-ray diagnosis is the signs and symptoms of AS have usually been established as long as 8–10 years prior to X-ray-evident changes occurring on a plain film X-ray, which means a delay of as long as 10 years before adequate therapies can be introduced. Options for earlier diagnosis are tomography and magnetic resonance imaging of the sacroiliac joints, but the reliability of these tests is still unclear. The Schober's test is a useful clinical measure of flexion of the lumbar spine performed during examination.

Treatment

Treatment of Ankylosing Spondylitis
The treatment of ankylosing spondylitis typically involves the use of medications to reduce inflammation and/or suppress immunity to stop progression of the disease, physical therapy, and exercise. Medications decrease inflammation in the spine and other joints and organs. Physical therapy and exercise help improve posture, spine mobility, and lung capacity.

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to decrease pain and stiffness of the spine and other joints. Commonly used NSAIDs include indomethacin (Indocin), tolmetin (Tolectin), sulindac (Clinoril), naproxen (Naprosyn), and diclofenac (Voltaren). Their common side effects include stomach upset, nausea, abdominal pain, diarrhea, and even bleeding ulcers. These medicines are frequently taken with food in order to minimize side effects.

In some people with ankylosing spondylitis, inflammation of joints excluding the spine (such as the hips, knees, or ankles) becomes the major problem. Inflammation in these joints may not respond to NSAIDs alone. For these individuals, the addition of medications that suppress the body's immune system is considered. These medications, such as sulfasalazine (Azulfidine), may bring about long-term reduction of inflammation. An alternative to sulfasalazine that is somewhat more effective is methotrexate (Rheumatrex, Trexall), which can be administered orally or by injection. Frequent blood tests are performed during methotrexate treatment because of its potential for toxicity to the liver, which can even lead to cirrhosis, and toxicity to bone marrow, which can lead to severe anemia.

Recent research has shown that for persistent ankylosing spondylitis with spinal involvement that is unresponsive to anti-inflammatory medications, both sulfasalazine and methotrexate are ineffective. Newer, effective medications for spine disease attack a messenger protein of inflammation called tumor necrosis factor (TNF). These TNF-blocking medications have been shown to be extremely effective for treating ankylosing spondylitis by stopping disease activity, decreasing inflammation, and improving spinal mobility. Examples of these TNF-blockers include etanercept (Enbrel), infliximab (Remicade), adalimumab (Humira), and golimumab (Simponi).

Prognosis

Prognosis of Ankylosing Spondylitis
The outlook for patients with ankylosing spondylitis is very much dependent upon the location and severity of its manifestations. The prognosis is best for those who maintain close monitoring with the treating doctors and who incorporate physical activities designed to maintain mobility. Quitting smoking is essential for the best long-term outcome.

Prevention

Prevention of Ankylosing Spondylitis
There is no prevention for this inherited (genetic) disease. Prevention measures are directed toward preventing complications of the disease with optimal treatments and monitoring for side effects of the treatments.