What Is Ankylosing Spondylitis?

Ankylosing spondylitis (AS) is a type of arthritis in which chronic inflammation primarily affects the back and neck (spine).

In severe cases, bones in the spine may fuse or adhere together (also referred to as ankylosis). These adhesions result in a rigid and inflexible spine. As a result, abnormal posture may be a consequence.

The condition can sometimes involve other joints, including the hips, knees, ankles, or shoulders. The disease may also systemically affect various organs—systemic means affecting the whole body, rather than a single body part.

This article explains ankylosing spondylitis symptoms, causes, diagnosis, and treatment.

Type of Arthritis

AS belongs to a group of conditions known as spondyloarthropathies.

Other spondyloarthropathies include:

• Reactive arthritis
• Psoriatic arthritis
• Enteropathic arthritis

Spondyloarthropathies are either axial or peripheral, depending on which joints are involved. Axial refers to conditions that involve the spine, whereas peripheral relates to diseases that affect other joints outside of the spine.

AS is an axial spondyloarthropathy.

Ankylosing Spondylitis Symptoms

Symptoms of AS usually start before the age of 45. They generally occur in stages.

Early Symptoms

The earliest symptoms of AS include:

• Pain and stiffness in the lower back region
• Pain that worsens following rest or inactivity and improves with activity
• Morning stiffness that lasts more than 30 minutes

Eventually, the pain and stiffness evolve and develop into chronic symptoms.

Chronic Symptoms

Over time, the pain and stiffness can progress up the spine to the neck. When this occurs, you might experience the following symptoms:

• The bones of the spine and neck may fuse
• Limited range of motion
• Decreased spine flexibility of the spine
• Shoulders, hips, and other joints may be involved

Hip, groin, or buttocks pain may make walking difficult. If your rib cage is involved, abnormal chest expansion may cause breathing difficulties. In addition, tendons and ligaments may be affected, resulting in Achilles tendonitis and plantar fasciitis.

Systemic Symptoms

AS is a systemic disease as well, meaning that people may develop whole-body symptoms, including:

• Fever
• Fatigue
• Eye inflammation
• Bowel inflammation
• Cardiovascular or lung problems (rare)

While anyone can develop AS, more men than women develop the disease. The age of disease onset is usually between 17 to 35 years old.

Causes

The condition's cause is unknown, but the genetic marker, HLA-B27, is present in 90% of people with the disease, suggesting a genetic connection. However, it's important to note that not everyone who has the HLA-B27 marker develops AS.

According to the Spondylitis Association of America, over 60 other genes or genetic markers make people susceptible to AS. Researchers believe that a triggering environmental event combined with genetic susceptibility causes the disease to develop.

Diagnosis

Healthcare providers base diagnosis on symptoms, a physical examination, blood tests, and imaging studies. Since early symptoms of ankylosing spondylitis can mimic other conditions, healthcare providers use diagnostic tests to rule out other rheumatic diseases.

If other tests do not show evidence of rheumatoid factor and rheumatoid nodules, this helps distinguish it from rheumatoid arthritis.

Blood Tests

While no single blood test can definitively diagnose AS, some tests provide important diagnostic clues. These tests include:

• HLA-B27 test
  
• Tests for nonspecific inflammation (sedimentation rate and CRP)

These tests help formulate the clinical picture, but they are not diagnostic. For example, while 95% of White people with AS have the HLA-B27 gene, only 50% of Black people with the condition have HLA-B27. Therefore, blood tests are an unreliable stand-alone diagnostic criterion.

Imaging

Imaging studies often show characteristic changes in the bones of the sacroiliac joints (space between the sacrum and the hip bone). These changes might be visible on the following:

• X-ray
• Magnetic resonance imaging (MRI)

Healthcare providers use X-rays to assess evidence of damage to the joints and spine. However, it may take years after the onset of symptoms to be observable. MRI can often detect them earlier than X-ray images.

Treatment

Treatment goals include reducing pain, stiffness, and inflammation, preventing deformity, and maintaining function and posture.

Pain Medications

Many medications treat AS. Nonsteroidal anti-inflammatory drugs (NSAIDs) are a first-line treatment for the condition, and many people use NSAID medication alone to manage it. However, when pain is not well-controlled by NSAIDs, analgesics, or pain medications may help.

Protein and Molecule Blockers

Tumor necrosis factor inhibitors (TNF-blockers) block a protein called TNFα to reduce inflammation. These medications have shown significant improvements in disease activity. They include:

• Humira (adalimumab)
• Remicade (infliximab)
• Enbrel (etanercept)
• Cimzia (certolizumab pegol)
• Simponi (golimumab)

In addition, Cosentyx (secukinumab), an IL-17 inhibitor (signaling molecule blocker), was approved in 2016 for treating AS.

JAK Inhibitors

Janus kinase inhibitors, also known as JAK inhibitors, target certain enzymes to taper down the effects of an overactive immune system. This eases pain and swelling and prevents joint damage.

The FDA approved JAK inhibitor Rinvoq (upadacitinib) in 2022 as a once-daily pill for adults with active AS who have had an inadequate response or intolerance to TNF blockers. It's important to note that the use of JAK inhibitors comes with some significant possible risks, including serious heart-related events, cancer, blood clots, and death.

DMARDs

DMARDs (disease-modifying antirheumatic drugs) slow disease progression. Typically, sulfasalazine helps people with AS and peripheral arthritis who cannot use a TNF blocker.

Methotrexate alone may help some people, but generally, it is inadequate for AS. Likewise, another DMARD, Arava (leflunomide), has little or no benefit for treating AS.

Corticosteroids

Rarely, healthcare providers prescribe a short-term course of oral corticosteroids. These should not be used long-term.

Physical Therapy

Physical therapy and exercise are a significant part of any treatment plan for AS. Exercise is essential for managing the disease and preserving mobility and function.

Prognosis

Some people have a mild disease course and can work and function normally. Others develop severe disease and live with many restrictions. They may qualify for disability benefits.

Typically, an individual deals with fluctuating disease activity that is manageable for the most part. A minority of people with the disease achieve a stage where symptoms diminish and go into remission.

If you have questions or concerns, talk with a healthcare provider. The treatment and coping strategies they offer can improve how you feel and your overall outcome.

Ankylosing Spondylitis Doctor Discussion Guide

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Coping

A spine that is fused or less flexible is more susceptible to fracture. Therefore, you must be mindful of the extra risk and take precautions. Be protective of your spine by limiting or avoiding behaviors that may increase your risk of falling, including:

• Limiting alcohol consumption
• Installing grab bars
• Picking up throw rugs in your house
• Avoiding high-impact activity
  

In addition, consider using a pillow that places your neck and back in good alignment while you rest or sleep. And always use your seat belt when driving or as a passenger in a vehicle.

People with AS who smoke should quit to lower their risk of breathing problems. And don't forget the importance of participating in an exercise program to strengthen your spine and improve your overall joint health.

Summary

Ankylosing spondylitis is a type of arthritis that affects the spine. Symptoms include pain, stiffness, and a limited range of motion. The condition is systemic, and can affect organ systems. AS is treated with medications that alleviate pain, reduce inflammation, and slow disease progression.

If the symptoms of ankylosing spondylitis are impacting your daily life, know that treatment options are available. Talk to your healthcare team about what medications or therapy programs are suitable for you.

Outside of medications, many people find that simple stretches and physical therapy go a long way in helping their bodies feel better. Start slow and explore moves that are right for you. It may take some time, but you may discover something helpful.