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Ankylosing Spondylitis

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Ankylosing Spondylitis and Pregnancy

Medical Author: William C. Shiel Jr., MD, FACP, FACR

The influence of pregnancy, delivery, and the post-partum period is a common concern of persons with arthritis and related conditions. Although ankylosing spondylitis occurs predominantly in men (two to three times more common in males than in females), women can and do develop the disease.

This topic of pregnancy and ankylosing spondylitis was studied and published under the title "Ankylosing spondylitis--the female aspect" (J Rheumatol 1998 Jan;25[1]:120-4). I think this study serves well as a review of pregnancy issues in women with ankylosing spondylitis.

In collaboration with the Ankylosing Spondylitis International Federation, a questionnaire including clinical data and details on past and recent pregnancies was sent to the female members of national and regional Ankylosing Spondylitis societies in the USA, Canada, and 11 European countries. (It should be noted that questionnaires do have shortcomings from a research standpoint, including inaccurate completion of the forms, lack of personal interaction, and accurate interpretation of both the questions and the responses.)

Nine hundred thirty-nine questionnaires were completed. The researchers found that the average age of the responding women at the onset of their ankylosing spondylitis was 23 years. In 21% of these women, the onset was related to a pregnancy, either occurring during or immediately after the pregnancy.

In this group, the frequency of accompanying features of ankylosing spondylitis was as follows: 45% had inflamed joints away from the spine (peripheral arthritis); 48% had inflammation of the iris of the eye (acute anterior uveitis); 18% had psoriasis; and 16% had inflammatory bowel disease.

Ankylosing spondylitis facts

  • Ankylosing spondylitis belongs to a group of arthritis conditions which tend to cause chronic inflammation of the spine (spondyloarthropathies).
  • Ankylosing spondylitis affects males two to three times more commonly than females.
  • Ankylosing spondylitis is a cause of back pain in adolescents and young adults.
  • The tendency to develop ankylosing spondylitis is genetically inherited.
  • The HLA-B27 gene can be detected in the blood of most patients with ankylosing spondylitis.
  • Ankylosing spondylitis can also affect the eyes, heart, lungs, and occasionally the kidneys.
  • The optimal treatment of ankylosing spondylitis involves medications that reduce inflammation or suppress immunity, physical therapy, and exercise.

What is 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.

Ankylosing spondylitis is two to three times more common in men than in women. In women, joints away from the spine are more frequently affected than in men. Ankylosing spondylitis affects all age groups, including children. When it affects children, it is referred to as juvenile ankylosing spondylitis. The most common age of onset of symptoms is in the second and third decades of life. Ankylosing spondylitis is often abbreviated AS and has been referred to as Bechterew's disease.

What causes 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.


Inflammation of Spondyloarthropathy Illustration - Picture of Ankylosing Spondylitis

How inflammation occurs and persists in different organs and joints in ankylosing spondylitis is a subject of active research. Each individual tends to have their own unique pattern of presentation and activity of the illness. The initial inflammation may be a result of an activation of the body's immune system, perhaps by a preceding bacterial infection or a combination of infectious microbes. Once activated, the body's immune system becomes unable to turn itself off, even though the initial bacterial infection may have long subsided. Chronic tissue inflammation resulting from the continued activation of the body's own immune system in the absence of active infection is the hallmark of an inflammatory autoimmune disease.



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