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What is juvenile ankylosing spondylitis (JAS)?

Juvenile ankylosing spondylitis (JAS) is a type of arthritis that affects the spine and the sites where the muscles, tendons, and ligaments are attached to bone. "Ankylosing" means stiff or rigid, "spondyl" means spine, and "itis" refers to inflammation.

  • JAS strikes young people, typically between ages 17 and 35, but it can occur in children and older adults as well.
  • JAS is thought to affect males two to three times more often than it does females.

JAS causes inflammation of the spine and large joints, resulting in stiffness and pain. The disease may result in:

  • erosion at the joint between the spine and the sacroiliac joint (hip bone)
  • bony bridges forming between vertebrae in the spine, fusing those bones together
  • bones in the chest may fuse

JAS is one of four disorders classified as spondyloarthropathies. The others are psoriatic arthritis, inflammatory bowel disease, and Reiter's syndrome. These disorders share features such as:

  • inflammation of the spine and sacroiliac joints
  • family history of the disease
  • similar non-arthritis symptoms
  • absence of rheumatoid factor (RF) in the blood (an antibody found in the blood of most, but not all, people who have rheumatoid arthritis, as well as other rheumatic diseases)

Juvenile Ankylosing Spondylitis | Symptoms & Causes

What are the symptoms of juvenile ankylosing spondylitis?

Symptoms of JAS tend to occur and disappear over periods of time. While each child may experience symptoms differently, some of the most common include:

  • back pain, usually most severe at night during rest
  • early morning stiffness
  • stooped posture in response to back pain (bending forward tends to relieve the pain)
  • inability to take a deep breath, if the joints between the ribs and spine are affected
  • appetite loss
  • weight loss
  • fatigue
  • fever
  • anemia
  • enthesitis (pain at the site of attachment of muscles, ligaments, and/or tendons to bone)
  • joint pain, particularly in the legs
  • vague pain, usually in the buttocks, thighs, heels, or near the shoulders
  • painful eye inflammation that causes redness and light sensitivity; your child may experience frequent recurrences of eye inflammation
  • organ damage, such as the heart, lungs, and eyes

Symptoms of juvenile ankylosing spondylitis may resemble other medical conditions or problems. Always consult your child's physician for a diagnosis.

What causes JAS?

JAS is considered to be a multifactorial condition, meaning that "many factors" are involved in causing it.

  • These factors are usually both genetic and environmental, and it takes both a combination of genes from both parents and unknown environmental factors to produce the condition.
  • Multifactorial traits do recur in families because they are partly caused by genes.
  • Often one gender (either males or females) is affected more frequently than the other in multifactorial traits.


There is a group of genes called HLA antigens that play a major role in whether your child will get a certain disease. The HLA antigen associated with JAS is called B27.

If your child has HLA-B27, she may have a genetic susceptibility (increased chance) of developing JAS. But it's important to remember that while most people with JAS do have HLA-B27, only a few people with HLA-B27 ever actually have JAS. This means your child may test positive for HLA-B27, but not have JAS.

Juvenile Ankylosing Spondylitis | Diagnosis & Treatments

How is juvenile ankylosing spondylitis diagnosed?

In addition to a complete medical history and physical examination, some of the diagnostic tests your child's doctor may order include:

  • x-rays: a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
  • erythrocyte sedimentation rate (ESR or sed rate): a measurement of how quickly red blood cells fall to the bottom of a test tube. When swelling and inflammation are present, the blood's proteins clump together and become heavier than normal. Thus, when measured, they fall and settle faster at the bottom of the test tube. Generally, the faster the blood cells fall, the more severe the inflammation.
  • detection of HLA-B27

How is juvenile ankylosing spondylitis treated?

The goal of treatment for JAS is to reduce pain and stiffness, prevent deformities, and help your child maintain as normal and active a lifestyle as possible.

Components of your child's treatment may include:

  • nonsteroidal anti-inflammatory medication (NSAIDs) to reduce pain and inflammation
  • short-term use of corticosteroids to reduce inflammation
  • attention to maintaining proper posture
  • regular exercise, including exercises that strengthen back muscles
  • physical therapy

How we care for juvenile ankylosing spondylitis

The Rheumatology Program at Boston Children's Hospital cares for children and adolescents with a broad range of rheumatologic and inflammatory diseases, including juvenile ankylosing spondylitis. As one of the largest and most experienced rheumatology programs in the United States, we see more than 3,000 children in our outpatient clinic each year. More than 600 children are treated on an inpatient (hospitalized) basis each year.

Juvenile Ankylosing Spondylitis | Programs & Services