Axial Spondyloarthritis: Causes, Symptoms and Treatment

What is Axial Spondyloarthritis?

Axial spondyloarthritis (axial SpA) is a chronic inflammatory rheumatic disease that primarily affects the spine and the sacroiliac joints (the joints connecting the pelvis to the lower spine). It belongs to the broader family of spondyloarthritides. Without adequate treatment, the disease can lead to progressive stiffening of the spine over time.

Axial SpA is divided into two subtypes:

• Radiographic axial SpA (r-axSpA): Also known as ankylosing spondylitis or Bechterew disease. Structural changes are visible on X-ray imaging.
• Non-radiographic axial SpA (nr-axSpA): Active inflammation is detectable by MRI, but no structural changes are yet visible on X-ray.

Causes and Risk Factors

The exact cause of axial spondyloarthritis is not yet fully understood. It is an autoimmune disease in which the immune system mistakenly attacks the body's own tissue. Key contributing factors include:

• Genetic predisposition: The HLA-B27 gene is present in over 90% of patients with ankylosing spondylitis and is a major genetic risk factor.
• Immunological factors: Pro-inflammatory cytokines such as TNF-alpha and Interleukin-17 (IL-17) drive joint inflammation.
• Environmental triggers: Infections, particularly of the gastrointestinal or urogenital tract, may trigger or worsen the disease.
• Age and sex: The disease typically begins in early adulthood (before age 45). Men are slightly more frequently affected than women.

Symptoms

The hallmark symptom of axial spondyloarthritis is chronic inflammatory back pain. This differs from mechanical back pain by several characteristic features:

• Onset of back pain before age 40
• Gradual onset over several weeks
• Improvement with exercise, but not with rest
• Morning stiffness lasting more than 30 minutes
• Pain in the second half of the night, causing the patient to wake up

Additional possible symptoms include:

• Sacroiliitis: Inflammation of the sacroiliac joints, causing pain in the buttocks or lower back
• Peripheral arthritis: Joint inflammation outside the spine, e.g. in the knees or hips
• Enthesitis: Inflammation at tendon insertion sites, commonly the heel
• Uveitis: Eye inflammation, particularly of the iris
• Psoriasis
• Inflammatory bowel diseases such as Crohn's disease or ulcerative colitis
• Elevated inflammatory markers in blood tests (CRP, ESR)

Diagnosis

The diagnosis of axial spondyloarthritis is based on a combination of clinical examination, laboratory tests, and imaging. The ASAS classification criteria (Assessment of SpondyloArthritis International Society) are the standard diagnostic framework:

Imaging

• MRI (Magnetic Resonance Imaging): The gold standard for early detection of active inflammation in the sacroiliac joints and spine, even before structural changes are visible on X-ray.
• X-ray: Detects structural damage such as syndesmophytes (bony bridges between vertebrae) or sacroiliitis, but only in later disease stages.

Laboratory Tests

• HLA-B27 testing: Detection of the genetic risk marker
• CRP and ESR: Inflammatory markers in the blood
• Exclusion of other conditions (e.g. rheumatoid factor for rheumatoid arthritis)

Treatment

Axial spondyloarthritis cannot be cured, but it can be effectively managed. The goals of therapy are to control inflammation, relieve pain, and preserve mobility.

Non-pharmacological Treatment

• Physiotherapy and regular physical exercise are the cornerstones of treatment. Posture correction and spinal mobilization exercises help slow the progression of stiffness.
• Patient education and self-management strategies
• Heat therapy to relieve stiffness

Pharmacological Treatment

• NSAIDs (Non-steroidal anti-inflammatory drugs) such as ibuprofen or diclofenac are the first-line treatment for mild to moderate symptoms.
• TNF inhibitors (e.g. adalimumab, etanercept): Biologics that block the pro-inflammatory TNF-alpha pathway, used when NSAIDs are insufficient.
• IL-17A inhibitors (e.g. secukinumab, ixekizumab): Newer biologics that specifically target interleukin-17.
• JAK inhibitors (e.g. tofacitinib, upadacitinib): Orally administered targeted therapies as an alternative to biologics.
• Corticosteroids are used only in specific situations (e.g. uveitis, local injections).

Surgical Treatment

In severe cases with significant joint damage, particularly of the hip, joint replacement surgery (arthroplasty) may be required.

Prognosis and Disease Course

The course of axial SpA varies considerably between individuals. Some patients experience mild symptoms with extended periods of remission, while others face a progressive course with increasing spinal stiffness. Early diagnosis and consistent treatment significantly improve long-term outcomes. With modern therapies, most patients are able to lead a largely normal life.

References

1. Sieper J, Poddubnyy D. Axial spondyloarthritis. Lancet. 2017;390(10089):73-84.
2. van der Heijde D, et al. ASAS/EULAR recommendations for the management of ankylosing spondylitis. Ann Rheum Dis. 2006;65(4):442-452.
3. Ward MM, et al. 2019 Update of the American College of Rheumatology/Spondylitis Association of America Recommendations for the Treatment of Ankylosing Spondylitis and Nonradiographic Axial Spondyloarthritis. Arthritis Rheumatol. 2019;71(10):1599-1613.