Ankylosing Spondylitis: Causes, Early Signs, and Symptoms
Learn about Ankylosing Spondylitis, its causes, early signs, and symptoms. Understand risk factors, diagnosis, and management strategies for this chronic inflammatory spine disease.
Written by Dr. Dhankecha Mayank Dineshbhai
Reviewed by Dr. M L Ezhilarasan MBBS
Last updated on 16th Sep, 2025
Introduction
Chronic back pain is common, but when does a persistent ache indicate something more systemic? Ankylosing Spondylitis (AS) is a complex inflammatory disease that primarily targets the spine, leading to pain, stiffness, and in severe cases, fusion of the vertebrae. Unlike typical mechanical back pain, AS is a lifelong condition with roots in genetics and the immune system. Understanding what leads to the signs of Ankylosing Spondylitis is the first step toward managing it effectively. This article explores the underlying causes, the range of symptoms, from classic back pain to less obvious systemic issues, and the factors that put certain individuals at higher risk, empowering you to recognise potential signs and seek expert guidance.
What is Ankylosing Spondylitis? Understanding the Disease
Ankylosing Spondylitis is a type of chronic inflammatory arthritis that falls under autoimmune diseases. "Ankylosing" means stiffening or fusing, and "spondylitis" refers to inflammation of the vertebrae. Essentially, AS is characterised by persistent inflammation that the body mistakenly directs at its own joints and ligaments, particularly where they attach to bone, a site called the enthesis.
The Body's Mistaken Attack: Autoimmunity Explained
In a healthy immune system, white blood cells protect against foreign invaders like viruses and bacteria. In autoimmune diseases such as AS, this system malfunctions. It cannot distinguish between foreign cells and the body's own tissues, particularly in the spine and sacroiliac joints at the base of the spine. This triggers a constant inflammatory response, damaging the affected areas.
The Hallmark of AS: Inflammation and Spinal Fusion
The body’s attempt to heal ongoing damage leads to AS’s defining feature. Over years of inflammation and repair, calcium deposits in spinal ligaments and joints may cause the vertebrae to fuse, resulting in loss of flexibility and the characteristic "bamboo spine" seen on X-rays. This fusion can lead to a forward-stooped posture if the disease is not managed proactively.
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The Root Causes: What Triggers Ankylosing Spondylitis?
The exact cause of AS is not singular but is believed to result from a combination of genetic predisposition and environmental factors that trigger the immune system's faulty response.
A. The Primary Suspect: The HLA-B27 Gene
The strongest link to developing AS is the presence of the HLA-B27 genetic marker. Research indicates that up to 90% of people with AS have this gene. It is a risk factor rather than a direct cause, and it may make the immune system react abnormally to certain gut bacteria.
Having the Gene Doesn't Guarantee the Disease
Most people carrying the HLA-B27 gene never develop AS. Only about 5-10% of HLA-B27 positive individuals get the disease, suggesting other factors are needed to trigger onset.
B. The Role of Environmental and Immune Triggers
Genetics loads the gun, but environmental factors may pull the trigger. Certain exposures are believed to initiate the autoimmune process in susceptible individuals.
1. Gut Bacteria and the Gut-Joint Axis
Research points to the microbiome—the community of bacteria in the intestines. Strains like Klebsiella pneumoniae may cross-react with the HLA-B27 protein, confusing the immune system and causing it to attack joints. This link explains why inflammatory bowel disease (IBD), such as Crohn’s or Ulcerative Colitis, is a common comorbidity with AS.
2. The Impact of Infections and Stress
Other triggers include previous gastrointestinal or genitourinary infections. Prolonged physical or emotional stress can also dysregulate the immune system and potentially contribute to the onset or flare-up of AS.
Recognising the Signs: Early and Common Symptoms
AS symptoms can be subtle initially and often resemble common back pain. Key differences help distinguish it.
The Classic Early Warning Signs
Inflammatory back pain is the cornerstone symptom. It typically includes:
- Gradual onset: Pain developing slowly over weeks or months
- Morning stiffness: Significant stiffness and pain in the lower back or hips lasting over 30 minutes after waking
- Improvement with activity: Pain eases with movement or exercise but worsens after inactivity
- Nocturnal pain: Pain that wakes you in the second half of the night
- Sacroiliac joint pain: Deep aching in the buttocks, sometimes alternating sides
Beyond the Back: Systemic and Extra-Articular Symptoms
AS can affect areas beyond the spine:
- Enthesitis: Pain where tendons or ligaments attach to bone (e.g., Achilles tendon, sole of the foot)
- Uveitis (Iritis): Sudden, painful red eye with light sensitivity and blurred vision; medical emergency
- Fatigue: Profound tiredness not relieved by sleep
- Joint pain and swelling: Knees, ankles, shoulders
- Digestive issues: Diarrhoea or abdominal pain linked to IBD
How is Ankylosing Spondylitis Diagnosed?
Early diagnosis is challenging because symptoms mimic other conditions. No single test confirms AS.
The Diagnostic Challenge: No Single Test
Diagnosis combines patient history, physical examination, imaging studies, and blood tests. Inflammatory back pain persisting over three months is a key starting point.
The Process: From Physical Exam to Imaging
Doctors assess spinal mobility, chest expansion, and pain in specific areas. They typically order:
- Imaging: X-rays and MRIs of sacroiliac joints and spine to detect inflammation, erosion, or fusion. MRI can detect early inflammation before X-rays show changes
- Blood tests: While no blood test confirms AS, markers like HLA-B27, ESR, and CRP are checked
If your symptoms align with AS, consulting a rheumatologist is crucial. Apollo24|7 offers online specialist consultations for initial evaluation and test guidance.
Who is at Risk? Key Ankylosing Spondylitis Risk Factors
Certain demographics and genetic profiles are associated with higher AS risk:
- Family history: Close relatives with AS increase risk
- Age: Onset typically in late adolescence to early adulthood (17–45 years)
- Sex: Men are historically diagnosed more often, but women may be underdiagnosed
- Presence of HLA-B27: The most significant genetic risk factor
Managing and Living with Ankylosing Spondylitis
While there is no cure, treatments control symptoms, reduce inflammation, and prevent complications.
Treatment Goals: Reduce Pain and Prevent Progression
Treatment is multidisciplinary:
- Medication: NSAIDs for pain and inflammation; DMARDs or biologics (TNF inhibitors) for severe cases
- Physical therapy: Maintains posture, flexibility, and chest expansion
- Lifestyle modifications: Regular exercise (swimming, stretching), quitting smoking, and heat/cold therapy
The Critical Role of Physical Therapy and Exercise
Daily exercise and targeted physiotherapy preserve spinal mobility, strengthen muscles, improve posture, and reduce pain. A sedentary lifestyle increases stiffness and risk of fusion.
Conclusion
Understanding what leads to the signs of Ankylosing Spondylitis empowers you to take a proactive role in spinal health. The journey begins with genetic predisposition and is often triggered by environmental factors, producing a wide spectrum of symptoms beyond simple backache. Recognising inflammatory back pain, its persistence, morning stiffness, and response to activity, is the critical first step. AS is lifelong but manageable. With modern treatments, including biologics and physiotherapy, most people with AS lead active lives. Do not dismiss persistent pain; seek medical advice for an accurate diagnosis and effective management. Apollo24|7 provides access to rheumatologists for comprehensive assessments.
Consult Top Rheumatologists
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Consult Top Doctors for Personalised Advice
Dr. T. N. Tamilselvam
Rheumatologist
20 Years • MBBS, MD, DM
Chennai
Apollo Speciality Hospitals Vanagaram, Chennai
(25+ Patients)
Dr. Tanmaya Kumar Sahu
General Physician/ Internal Medicine Specialist
12 Years • MBBS, MD ( Internal Medicine )
Bhubaneswar
Apollo Hospitals Old Sainik School Road, Bhubaneswar
Dr. Anand Ravi
General Physician
2 Years • MBBS
Bengaluru
PRESTIGE SHANTHINIKETAN - SOCIETY CLINIC, Bengaluru
Dr. Zulkarnain
General Physician
2 Years • MBBS, PGDM, FFM
Bengaluru
PRESTIGE SHANTHINIKETAN - SOCIETY CLINIC, Bengaluru
Dr. Thorana Prakash M
General Physician
2 Years • MBBS
Bengaluru
PRESTIGE SHANTHINIKETAN - SOCIETY CLINIC, Bengaluru
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Frequently Asked Questions
At what age does ankylosing spondylitis typically start?
AS most commonly begins in late adolescence or early adulthood (17–45 years) but can occasionally start in childhood or later life.
Can you test for the HLA-B27 gene at home?
Genetic testing kits exist, but results must be interpreted clinically by a doctor. A positive result alone does not confirm AS. Consult a rheumatologist, and Apollo24|7 offers home blood collection when advised.
What is the difference between arthritis and spondylitis?
'Arthritis' is general joint inflammation. 'Spondylitis' refers specifically to inflammation of spinal vertebrae. Ankylosing Spondylitis primarily affects the spine.
Is ankylosing spondylitis a disability?
Advanced AS can cause spinal fusion, postural deformity, and chronic pain, potentially qualifying as disabling. Early treatment aims to prevent severe progression.
What does an ankylosing spondylitis flare-up feel like?
A flare-up involves worsening inflammatory back pain, stiffness, extreme fatigue, and sometimes swelling in other joints. Flares are managed by adjusting medication and rest.