Ankylosing Spondylitis

A chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints

Table of Contents

Quick Facts

  • Type: Inflammatory Arthritis
  • ICD-10: M45
  • Prevalence: ~0.5% of adults
  • Onset: Typically 20-40 years

Overview

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints, the areas where the spine connects to the pelvis. This condition belongs to a group of related diseases called spondyloarthritis. The inflammation can eventually lead to new bone formation, causing vertebrae to fuse together, resulting in a rigid, inflexible spine.

The name "ankylosing spondylitis" comes from the Greek words "ankylos" (meaning stiffening of a joint) and "spondylos" (meaning vertebrae). The condition typically begins in the sacroiliac joints and lower spine, gradually progressing upward. While the spine is the primary target, AS can also affect other joints, including hips, shoulders, knees, and ankles.

AS is more common in men than women, with a ratio of approximately 3:1, and typically begins in early adulthood. The condition has a strong genetic component, with about 90% of patients testing positive for the HLA-B27 gene. Early diagnosis and appropriate treatment can help manage symptoms, slow disease progression, and maintain mobility and quality of life.

Symptoms

The symptoms of ankylosing spondylitis typically develop gradually over months or years. Early symptoms may be mild and intermittent, making the condition challenging to diagnose in its initial stages.

Primary Symptoms

Low Back Pain

Chronic pain in the lower back and buttocks, often worse at rest

 Hip Pain

Pain and stiffness in the hip joints, particularly in the morning

 Morning Stiffness

Severe stiffness lasting more than 30 minutes after waking

 Leg Pain

Radiating pain down the legs, especially during inflammation

Additional Symptoms

  • Knee pain and stiffness
  • Elbow pain and inflammation
  • Numbness and tingling (paresthesia) in arms and legs
  • Generalized body aches and pain
  • Fatigue and reduced energy levels
  • Loss of appetite and weight loss
  • Low-grade fever

Advanced Symptoms

As the condition progresses, additional symptoms may develop:

  • Reduced spinal flexibility and mobility
  • Stooped posture (kyphosis)
  • Difficulty breathing due to chest wall involvement
  • Eye inflammation (uveitis) - occurs in about 40% of patients
  • Heart problems, including aortic valve issues
  • Lung complications from reduced chest expansion
  • Bowel inflammation

Characteristic Pattern

AS symptoms typically follow a distinctive pattern:

  • Pain and stiffness are worse in the morning and after periods of inactivity
  • Symptoms improve with movement and exercise
  • Pain often awakens patients in the second half of the night
  • Symptoms may flare and subside in cycles

Causes

The exact cause of ankylosing spondylitis is not fully understood, but research has identified several key factors that contribute to its development:

Genetic Factors

Genetics play a crucial role in AS development:

  • HLA-B27 Gene: About 90% of people with AS carry this gene, though only 5-10% of HLA-B27 carriers develop the condition
  • Other genes: IL23R, ERAP1, and several other genes have been associated with increased AS risk
  • Family history: Having a close relative with AS increases risk by 10-20 times

Immune System Dysfunction

AS is an autoimmune condition where the immune system mistakenly attacks healthy tissues:

  • The immune system targets the entheses (where ligaments and tendons attach to bone)
  • Chronic inflammation leads to bone erosion followed by new bone formation
  • This process can eventually cause vertebrae to fuse together

Environmental Triggers

While genetics predispose to AS, environmental factors may trigger its onset:

  • Infections: Bacterial infections, particularly those affecting the gut or genitourinary tract
  • Stress: Physical or emotional stress may precipitate flares
  • Trauma: Physical injury to the spine may trigger inflammation in susceptible individuals

Molecular Mimicry Theory

Some researchers believe that certain bacteria share molecular structures similar to HLA-B27, causing the immune system to attack both the bacteria and the body's own tissues in a case of mistaken identity.

Risk Factors

Several factors increase the likelihood of developing ankylosing spondylitis:

Non-Modifiable Risk Factors

  • Genetics: Carrying the HLA-B27 gene significantly increases risk
  • Gender: Men are 2-3 times more likely to develop AS than women
  • Age: Onset typically occurs between ages 20-40
  • Ethnicity: More common in people of Northern European and Scandinavian descent
  • Family history: Having relatives with AS or related conditions

Associated Conditions

Having certain conditions may increase AS risk:

Potential Environmental Factors

  • Certain bacterial infections (Klebsiella, Salmonella)
  • Smoking (may worsen symptoms and progression)
  • Physical trauma to the spine
  • High levels of physical or emotional stress

Diagnosis

Diagnosing ankylosing spondylitis can be challenging, especially in early stages. There is no single test for AS, so doctors use a combination of clinical assessment, imaging, and laboratory tests.

Clinical Assessment

  • Medical history: Duration and pattern of symptoms, family history
  • Physical examination: Spine flexibility tests, joint examination
  • Symptom evaluation: Inflammatory back pain criteria assessment

Imaging Studies

  • X-rays: Show sacroiliac joint changes and spinal fusion in advanced cases
  • MRI: Can detect early inflammation before X-ray changes appear
  • CT scan: Provides detailed bone structure images when needed

Laboratory Tests

  • HLA-B27: Present in ~90% of AS patients but not diagnostic alone
  • C-reactive protein (CRP): Indicates inflammation levels
  • Erythrocyte sedimentation rate (ESR): Measures inflammation
  • Complete blood count: Rules out other conditions

Diagnostic Criteria

The Assessment of Spondyloarthritis International Society (ASAS) criteria include:

  • Sacroiliitis on imaging plus one spondyloarthritis feature, OR
  • HLA-B27 plus two spondyloarthritis features

Differential Diagnosis

Conditions that may be confused with AS include:

Treatment Options

While there is no cure for ankylosing spondylitis, various treatments can effectively manage symptoms, reduce inflammation, and slow disease progression. Treatment typically involves a combination of medications, physical therapy, and lifestyle modifications.

Medications

First-Line Treatments:

  • NSAIDs: Ibuprofen, naproxen, or celecoxib to reduce inflammation and pain
  • Physical therapy: Essential for maintaining mobility and posture

Advanced Therapies:

  • TNF inhibitors: Etanercept, adalimumab, infliximab for severe cases
  • IL-17 inhibitors: Secukinumab, ixekizumab for TNF-resistant cases
  • JAK inhibitors: Tofacitinib for refractory cases
  • Sulfasalazine: May help with peripheral arthritis
  • Corticosteroids: Short-term use for severe flares

Physical Therapy and Exercise

  • Range of motion exercises: Maintain spinal flexibility
  • Strengthening exercises: Support spinal muscles
  • Postural training: Prevent spinal deformity
  • Breathing exercises: Maintain chest expansion
  • Swimming: Low-impact full-body exercise

Surgical Interventions

Surgery may be considered in severe cases:

  • Hip replacement: For severe hip joint damage
  • Spinal osteotomy: To correct severe spinal deformity
  • Vertebroplasty: For spinal fractures

Complementary Therapies

  • Massage therapy for muscle tension relief
  • Acupuncture for pain management
  • Heat and cold therapy
  • TENS (transcutaneous electrical nerve stimulation)

Prevention

While ankylosing spondylitis cannot be prevented due to its genetic nature, certain strategies can help reduce the risk of flares and slow disease progression:

Primary Prevention Strategies

  • Maintain good posture: Practice proper sitting and standing posture
  • Regular exercise: Stay physically active to maintain joint mobility
  • Avoid smoking: Smoking can worsen AS symptoms and complications
  • Manage infections promptly: Treat bacterial infections quickly
  • Stress management: Use techniques to reduce physical and emotional stress

For High-Risk Individuals

People with HLA-B27 or family history should:

  • Be aware of early AS symptoms
  • Seek medical attention for persistent back pain
  • Maintain an active lifestyle
  • Consider genetic counseling when planning families

Preventing Complications

  • Eye exams: Regular screening for uveitis
  • Bone density tests: Monitor for osteoporosis
  • Cardiovascular monitoring: Regular heart health checkups
  • Pulmonary function tests: Monitor breathing capacity

When to See a Doctor

Early diagnosis and treatment of ankylosing spondylitis are crucial for preventing complications and maintaining quality of life.

Seek Immediate Medical Attention

  • Sudden severe back pain following trauma
  • Acute eye pain, redness, or vision changes (possible uveitis)
  • Severe difficulty breathing or chest pain
  • Signs of spinal fracture (severe pain, neurological symptoms)
  • Fever with severe joint pain

Schedule an Appointment

  • Chronic back pain lasting more than 3 months, especially if:
    • Worse in the morning and improves with activity
    • Awakens you from sleep in the second half of the night
    • Associated with morning stiffness lasting >30 minutes
  • Family history of AS and developing back pain
  • Persistent hip, knee, or ankle pain and stiffness
  • Recurring eye inflammation
  • Inflammatory bowel symptoms with joint pain

Follow-up Care

If diagnosed with AS, regular follow-up is essential:

  • Monitor disease progression and treatment response
  • Adjust medications as needed
  • Screen for complications
  • Update physical therapy programs

Related Conditions

Ankylosing spondylitis is part of a group of related conditions called spondyloarthritis. Several other conditions are commonly associated with AS:

Psoriatic Arthritis

Inflammatory arthritis associated with psoriasis

 Reactive Arthritis

Arthritis triggered by infections

 Inflammatory Bowel Disease

Crohn's disease and ulcerative colitis

 Uveitis

Eye inflammation affecting AS patients

Other Associated Conditions

Frequently Asked Questions

Is ankylosing spondylitis hereditary?

AS has a strong genetic component. About 90% of people with AS carry the HLA-B27 gene, and having a family member with AS increases your risk significantly. However, having the gene or family history doesn't guarantee you'll develop the condition - only 5-10% of HLA-B27 carriers actually develop AS.

Can ankylosing spondylitis be cured?

Currently, there is no cure for ankylosing spondylitis. However, with proper treatment including medications, physical therapy, and lifestyle modifications, many people with AS can manage their symptoms effectively and maintain a good quality of life. Early diagnosis and treatment are key to preventing complications.

Will I end up in a wheelchair?

Most people with AS do not become wheelchair-bound. While severe cases can lead to significant spinal fusion and mobility limitations, modern treatments are very effective at slowing disease progression. Regular exercise, proper treatment, and early intervention help maintain mobility and function.

What exercises are best for ankylosing spondylitis?

The best exercises for AS include swimming, walking, yoga, tai chi, and specific stretching routines. Range of motion exercises for the spine and breathing exercises are particularly important. Always consult with a physical therapist experienced in AS to develop a safe, effective exercise program tailored to your needs.

Can diet affect ankylosing spondylitis?

While no specific diet can cure AS, some people find that reducing inflammatory foods (processed foods, sugar, refined carbohydrates) and increasing anti-inflammatory foods (omega-3 fatty acids, fruits, vegetables) may help manage symptoms. Maintaining a healthy weight also reduces stress on joints.

Medical Disclaimer: This information is for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of ankylosing spondylitis or any medical condition. If you're experiencing severe back pain or related symptoms, seek medical attention promptly.

References

  1. Sieper J, Poddubnyy D. Axial spondyloarthritis. Lancet. 2017;390(10089):73-84.
  2. Ward MM, Deodhar A, Gensler LS, et al. 2019 Update of the American College of Rheumatology/Spondylitis Association of America/Spondyloarthritis Research and Treatment Network Recommendations for the Treatment of Ankylosing Spondylitis and Nonradiographic Axial Spondyloarthritis. Arthritis Rheumatol. 2019;71(10):1599-1613.
  3. Rudwaleit M, van der Heijde D, Landewe R, et al. The Assessment of SpondyloArthritis International Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general. Ann Rheum Dis. 2011;70(1):25-31.
  4. Braun J, Sieper J. Ankylosing spondylitis. Lancet. 2007;369(9570):1379-1390.
  5. European League Against Rheumatism. EULAR recommendations for the management of ankylosing spondylitis. Ann Rheum Dis. 2023.