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An Updated Overview Of Spondyloarthritis, A Family Of Related Diseases

A Question and Answer with Dr. Jessica Walsh

By Jessica Walsh, MD

We hear a few different terms to describe ankylosing spondylitis (AS) and related diseases: Spondyloarthritis, spondyloarthritides and spondyloarthropathy. . . Is there a difference?

Spondyloarthritis and spondyloarthropathy are often used interchangeably. Some experts prefer the term spondyloarthritis rather than spondyloarthropathy because the ending "arthritis" indicates inflammation of the joint, whereas the ending "arthropathy" can refer to any type of joint disease. Inflammation is a key feature that helps distinguish spondyloarthritis from other types of arthritis, including wear-and-tear arthritis, such as osteoarthritis. Spondyloarthritides is the plural form of spondyloarthritis.

How is this group of diseases related? Why is it sometimes called a "family" of conditions?

These diseases look and behave in similar ways because they share overlapping disease features. Common features of spondyloarthritis include inflammation in the spine, pelvis, other joints, intestine, eyes [Editor's note: please see side bar on Uveitis / Iritis to the right], and heels. This family of diseases is divided into individual categories according to the predominant disease feature(s). For example, inflammation of the intestine can occur with any type of spondyloarthritis, but is most pronounced in patients with IBDassociated arthritis (also called enteropathic arthritis).

What does "seronegative" mean? How does it relate to this group of diseases?

Seronegative means that specific blood tests used to help diagnose rheumatoid arthritis are negative. In some instances, these blood tests are helpful in determining whether a person has rheumatoid arthritis or spondyloarthritis. In most cases, a diagnosis of spondyloarthritis can be made without these blood tests.

Is ankylosing spondylitis (AS) considered the "primary" disease? Why or why not?

For people with ankylosing spondylitis, it is the primary disease. For people with other types of spondyloarthritis, it is not.

In the past, ankylosing spondylitis has been portrayed as the primary type of spondyloarthritis for several reasons including the following:
  • Ankylosing spondylitis is easier to study than reactive arthritis and IBD-associated arthritis because it is much more common.
  • Ankylosing spondylitis is often easier for doctors and patients to recognize than undifferentiated spondyloarthritis and reactive arthritis.
  • Ankylosing spondylitis has been recognized as a unique type of arthritis for hundreds of years, whereas other types of spondyloarthritis were described more recently. For example, psoriatic arthritis was not widely recognized as a distinct form of arthritis until the 1960s.

Can you give us a key symptom or "feature" of each of the conditions in this group? What makes each one distinct or different from the others?

Ankylosing Spondylitis (AS)

Inflammation in the pelvis and/or spine causes inflammatory back pain. Inflammatory back pain usually starts gradually before the age of 40, tends to improve with activity but not rest, and occurs with stiffness in the morning that lasts at least 30 minutes.

Reactive Arthritis (Reiter's Syndrome - ReA)

An infection in the intestine or urinary tract usually occurs before inflammation in the joints.

Juvenile Spondyloarthritis (JSpA)

Symptoms begin in childhood. JSpA can look like any other type of spondyloarthritis. Enthesitis (inflammation where tendons or ligaments meet bone) is often a dominant disease feature.

Arthritis Associated With Inflammatory Bowel Disease (Enteropathic Arthritis - EnA)

Inflammation of the intestine is a predominant feature. Symptoms may include chronic diarrhea, abdominal pain, weight loss, and/or blood in the stool. The most common types of inflammatory bowel disease are Crohn's, ulcerative colitis, and undifferentiated colitis.

Psoriatic Arthritis (PsA)

PsA frequently causes pain and swelling in the small joints of the hands and feet. Most people with PsA have a psoriasis skin rash. Some people have a "sausage digit" with a toe or finger that swells between the joints as well as around the joints.

Undifferentiated Spondyloarthritis (USpA)

People with USpA have symptoms and disease features consistent with spondyloarthritis, but their disease doesn't fit into another category of spondyloarthritis. For example, an adult may have iritis, heel pain (caused by enthesitis), and knee swelling, WITHOUT back pain, psoriasis, a recent infection, or intestinal symptoms. This person's combination of disease features suggests spondyloarthritis, but he or she doesn't fit into the categories of ankylosing spondylitis, psoriatic arthritis, reactive arthritis, juvenile spondyloarthritis or IBD-associated arthritis.

Can one of these conditions share symptoms or complications with another one of the conditions? In general terms, do symptoms overlap? If so, how? What are the main similarities - if any?

Absolutely. The main similarities that can occur with any type of spondyloarthritis are:
  • Inflammation in the pelvis and spine that usually causes inflammatory back pain.
  • Pain and/or swelling of any other joint in the body (hips, knees, ankles, feet, hands, wrists, elbows, shoulders etc.)
  • Sudden onset of marked pain and redness in one eye at a time (uveitis/iritis).
  • Psoriasis skin rash.
  • Inflammation in the intestine (Crohn's, ulcerative colitis, undifferentiated colitis).
  • Inflammation along the tendons of the finger or toes (sausage digits, also called dactylitis).
  • Inflammation where tendons and ligaments meet the bone (enthesitis). This commonly occurs at the back or bottom of the heel.

Why would a doctor diagnose one form of spondyloarthritis over another?

Doctors classify people as having a certain type of spondyloarthritis according to the predominant disease feature(s). For example, a person with psoriasis and joint swelling in the hands and feet will most likely be classified as having psoriatic arthritis. A person with inflammatory back pain and x-ray changes consistent with inflammation in the sacroiliac joints in the pelvis will likely be classified as having ankylosing spondylitis. A person with Crohn's and swelling in the knees and ankles most likely has IBD-associated arthritis. Sometimes, disease features are equally dominant and a person may fit into more than one type of spondyloarthritis. For example, a person could have psoriasis, inflammation in the pelvis/spine, and Crohn's disease. This person could correctly be said to have any of the following:
  • Psoriatic arthritis with ankylosing spondylitis and Crohn's.
  • Ankylosing spondylitis with psoriasis and Crohn's.
  • IBD-associated arthritis with ankylosing spondylitis and psoriasis.

Can a diagnosis change from, say, undifferentiated spondyloarthritis (USpA) to ankylosing spondylitis or another one of these conditions? Why would this occur?

Yes. The diseases can evolve or change over time, since not all symptoms occur at once. For example, the previously discussed person with USpA with iritis, enthesitis, and knee swelling could develop back pain and inflammatory changes on x-rays that would lead to the diagnosis of ankylosing spondylitis.

Q: Are men and women affected at different rates between these diseases? Can you give us some details on how these rates were determined?

Similar numbers of men and women are affected with spondyloarthritis. In the past, it was thought that ankylosing spondylitis was more common in men than women. More recent studies suggest that ankylosing spondylitis occurs in similar numbers of men and women. Early estimates of the occurence of ankylosing spondylitis suggested that ankylosing spondylitis occurred 9-10 times more frequently in men than women. However, there were problems with how these early studies were done. More recent studies reported that men are 2 to 3 times more likely than women to have ankylosing spondylitis. These studies use relatively narrow definitions of ankylosing spondylitis that rely on classic manifestations of inflammatory back pain and damage on x-rays. Classic inflammatory back pain may be the initial symptom in men more frequently than in women, and women may have less x-ray damage than men. Despite these differences, the overall disease severity is similar in men and women.

When broader definitions are used to identify people with spondyloarthritis in the pelvis and/or spine (axial spondyloarthritis), the prevalence is similar in men and women.

How are these conditions treated? Are there any notable differences in treatment such as prescribed medications?

There are several treatment options for various types of spondyloarthritis. The treatments for each disease overlap, but they are not identical. For example, certain treatments may simultaneously help with psoriasis, inflammatory bowel disease, enthesitis, and arthritis. Other treatments may help with one or two disease features, but not the others. There are even some treatments that may help with one disease feature, but make another feature worse. Treatments need to be tailored for each individual, according to the type and severity of specific disease features. Many other factors must also be considered when selecting therapies, including other medical conditions, access to therapies, and the preferences of patients.

Please see our medications guide for more information.

Is there a known cause for these diseases?

We know that there are several specific genes that increase the risk of developing spondyloarthritis. HLA-B27 is the best studied gene and it associates most strongly with inflammation in the pelvis (sacroiliac joints) and spine. Most people with HLA-B27 and other high risk genes never develop spondyloarthritis. We don't yet understand why some people develop disease and others don't. There are also studies suggesting that things in our environment may cause disease. For example, specific types of infections may trigger disease. However, environmental triggers are not known for most people who develop spondyloarthritis. There is much research that needs to be done to better understand why certain people get these diseases.

Is there a cure?

Not yet…

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Jessica Walsh, MD

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