What is juvenile ankylosing spondylitis?

Ankylosing spondylitis (AS) is a type of arthritis that affects the lower back and spine. Patients with AS can also have tenderness where the muscles, tendons, and ligaments attach to bone (enthesitis). AS that begins before age 18 is called juvenile ankylosing spondylitis (JAS).

About 10-20 percent of people with AS begin to have symptoms before age 18.

The condition’s name comes from its symptoms:

• Ankylosing means stiff or rigid.
• Spondyl means spine.
• Itis refers to inflammation.

Ankylosing spondylitis causes inflammation of the spine, lower back (sacroiliac joint), and large joints resulting in stiffness and pain. It may also cause new bone formation across the involved joints in the spine and/or lower back.  This new bone formation essentially fuses the joint(s) together, causing restricted range of motion.

Many children with juvenile ankylosing spondylitis also have intestinal inflammation or inflammatory bowel disease. Symptoms suggestive of inflammatory bowel disease include abdominal pain, blood in the stool and weight loss.

Both genetic and environmental factors cause JAS. It tends to run in families and males are three times more likely to be affected by JAS than females.

Signs and symptoms

The signs and symptoms experienced by children and adolescents with juvenile ankylosing spondylitis vary. The most common symptoms include:

• Morning stiffness
• Pain in the back or buttocks that improves with activity
• Pain in the knees, heels or bottom of the feet that gets worse with activity
• Swelling of the large joints of the lower extremities
• Trouble standing up straight or touching toes
• Abdominal symptoms (pain, diarrhea, weight loss)
• Fatigue
• Eye pain, redness, and sensitivity to light

Many symptoms of JAS are also common in other diseases and medical conditions. Always consult your child's doctor or a specialist for an accurate diagnosis.

Testing and diagnosis

Diagnostic evaluation begins with a thorough medical history and physical examination of your child. At The Children’s Hospital of Philadelphia, clinical experts use a variety of diagnostic tests to diagnose juvenile ankylosing spondylitis and possible complications, including:

Imaging

• X-ray of the pelvis and/or spine. A diagnostic test that uses invisible electromagnetic energy beams to produce images of the lower back, hips, and spine onto film. These x-rays allow your physician to assess for damage to the joints.
• MRI of the pelvis. A diagnostic test that does not involve radiation and allows your physician to assess for active/ongoing inflammation in the lower back, hip, and spine.
• Ultrasound. This test can be done in the clinic by your rheumatologist to assess for inflammation of the joints and the tendon insertions. This test does not work well to assess for inflammation of the joints of the lower back or spine.

Blood tests

• Complete blood count. This test allows for assessment of anemia, or low blood counts. Anemia can be secondary to chronic inflammation from JAS or slow blood loss from the gut if there is accompanying intestinal inflammation. This test also checks the white cell and platelet count. Platelets can be elevated when there is inflammation.
• Comprehensive metabolic panel. This test allows for assessment of electrolytes and intestinal inflammation. If there is intestinal inflammation the liver enzymes may be high and the albumin (measure of protein) may be low.
• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR or sed rate). These tests are done to determine if there is inflammation in the body. Children with JAS often have an elevated CRP and/or ESR at diagnosis or continued disease activity.
• HLA-B27 antigen. HLA-B27 is an antigen that is present in about 8 percent of normal, healthy people. Only 1 in 20 people who are HLA B27+ develop ankylosing spondylitis.  That proportion increases to 1 in 5 if there is an affected parent (or other first-degree relative).

Treatments

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

Specific treatment for juvenile ankylosing spondylitis will be determined by your child's doctor based on:

• Your child's overall health and medical history
• Extent of the condition
• Your child's tolerance for specific medications, procedures, and therapies
• Expectation for the course of the disease
• Your opinion or preference

Treatment may include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain and inflammation.
• Short-term use of oral steroids to reduce inflammation.
• Injection of steroids directly into the affect joint(s).
• Disease-modifying anti-rheumatic drugs (DMARDS) such as methotrexate or sulfasalazine for arthritis. These medications do not work, however, for arthritis of the spine or lower back.
• Biologic medications such as infliximab, adalimumab, or etanercept. These medications help improve arthritis all over the body and also help reduce inflammation in the spine and lower back.
• Regular exercise, including exercises that strengthen the abdominal and back muscles.
• Physical therapy.

Follow-up care

Children with JAS should be routinely monitored by a pediatric rheumatologist (every 4-6 months) and an ophthalmologist (yearly).