Ankylosing spondylitis (AS) is a chronic immune-mediated inflammatory condition that primarily affects the sacroiliac joints and spine. It leads to progressive stiffness, pain, and sometimes spinal fusion.
💡 It is the classic example of a seronegative spondyloarthropathy, strongly linked with HLA-B27.
Inflammation begins at the entheses (where tendons/ligaments insert into bone)
Causes bone erosion followed by abnormal new bone formation
Leads to progressive ankylosis (fusion) of spinal joints
Strong genetic link: HLA-B27 positivity in most patients
🚨 Advanced disease can result in a rigid “bamboo spine” with severe restriction of movement.
Male sex (≈3:1)
Onset usually before 40 (peak in 20s)
Family history of AS
HLA-B27 positivity
Spinal and axial symptoms:
Chronic back pain with insidious onset
Morning stiffness lasting >30 minutes, improving with exercise
Alternating buttock pain (sacroiliitis)
Reduced spinal flexibility
Examination findings:
Loss of lumbar lordosis
Restricted chest expansion
Positive Schober’s test
Extra-articular features:
Acute anterior uveitis (painful red eye, photophobia)
Aortic regurgitation and conduction problems
Apical pulmonary fibrosis
Links with IBD and psoriasis
🚨 Red eye with pain and photophobia in an AS patient should trigger urgent ophthalmology referral.
Blood tests: raised ESR/CRP, HLA-B27 may be positive
Imaging:
X-ray: bilateral sacroiliitis in established disease
MRI: detects early sacroiliitis and bone marrow oedema
Functional tests: reduced chest expansion, limited lumbar movement
💡 MRI is the most sensitive tool for early diagnosis.
Lifestyle and physiotherapy: exercise is the cornerstone, with postural training and stretching critical to long-term function
Pharmacological:
NSAIDs are first-line for pain and stiffness
Biologic therapy (anti-TNF or IL-17 inhibitors) if symptoms persist despite NSAIDs
Support: smoking cessation, patient education, referral to physiotherapy and rheumatology
🚨 Systemic steroids have limited value in AS and are generally avoided long-term.
Progressive spinal fusion and disability
Uveitis (up to 40%)
Cardiac disease: aortic regurgitation, conduction abnormalities
Restrictive lung disease
Increased risk of spinal fractures, even with minor trauma
Highly variable; early diagnosis and biologic treatment can slow progression
Worse outcomes with smoking, early hip involvement, or delayed diagnosis
Fries Tips
Think AS in a young man with back pain improving with exercise
Always ask about eye symptoms — uveitis is a key extra-articular feature
MRI of sacroiliac joints is best for early detection
NSAIDs first; escalate to biologics if persistent disease
Daily mobility exercises are as important as medication
