What Causes Ankylosing Spondylitis? Understanding Triggers, Risk Factors, and Prevention

Ankylosing spondylitis (AS), commonly referred to as spinal arthritis, is a chronic inflammatory condition primarily affecting the spine and sacroiliac joints. While the exact cause remains complex, research indicates that genetic predisposition plays a central role. Individuals with a specific gene variant known as HLA-B27 are significantly more susceptible to developing this condition. A simple blood test available at most medical facilities can detect the presence of HLA-B27. A positive result doesn't guarantee disease onset but strongly suggests increased vulnerability, especially when combined with other environmental or immunological triggers.

Genetic Susceptibility and Immune System Response

The link between HLA-B27 and ankylosing spondylitis has been well-documented in clinical studies. This gene variant influences how the immune system responds to certain pathogens, sometimes leading to autoimmune reactions where the body mistakenly attacks its own tissues—particularly those in the spine and pelvis. However, not everyone with HLA-B27 develops AS, indicating that genetics alone aren't sufficient to trigger the disease. Environmental factors often act as catalysts in genetically prone individuals.

The Role of Bacterial Infections: Klebsiella Pneumoniae Connection

Emerging research highlights a strong association between ankylosing spondylitis and bacterial infections, particularly Klebsiella pneumoniae. This type of bacteria, often found in the gut microbiome, may provoke an abnormal immune response in HLA-B27-positive individuals. Molecular mimicry—a phenomenon where bacterial proteins resemble human tissue proteins—can confuse the immune system, leading it to attack spinal ligaments and joints. Gastrointestinal infections or dysbiosis (microbial imbalance) may therefore precede or exacerbate symptoms of AS, suggesting that gut health plays a critical role in disease development.

Gender and Age: Who Is Most at Risk?

Ankylosing spondylitis exhibits a clear gender disparity. Men are up to 10 times more likely to be diagnosed than women, although recent data suggests that female cases may be underreported due to milder or atypical symptoms. The typical onset occurs during early adulthood, most commonly between the ages of 18 and 50. Because symptoms often begin subtly—such as persistent lower back pain or morning stiffness—many patients experience delays in diagnosis. Early detection is crucial for managing progression and maintaining quality of life.

Environmental and Lifestyle Influences

Beyond genetics and infection, lifestyle and environmental factors can influence the likelihood of developing ankylosing spondylitis. Chronic stress, smoking, poor posture, and sedentary habits may worsen inflammation and joint damage. Conversely, regular physical activity, anti-inflammatory diets, and proper sleep hygiene have shown benefits in reducing flare-ups and improving mobility. Urban living conditions, pollution exposure, and occupational hazards may also contribute to immune dysregulation over time.

Taking Proactive Steps Toward Prevention and Management

While ankylosing spondylitis cannot yet be prevented outright, understanding personal risk factors empowers individuals to take control of their health. Those with a family history of autoimmune disorders or a confirmed HLA-B27 status should consider routine monitoring, maintain a healthy gut microbiome, avoid smoking, and engage in spine-friendly exercises like swimming or yoga. Consulting a rheumatologist at the first sign of chronic back pain can lead to earlier intervention and better long-term outcomes.