Ankylosing Spondylitis Flashcards
What is ankylosing spondylitis (AS), and what is its typical presentation?
Ankylosing spondylitis is a chronic inflammatory arthritis of the spine that typically presents in young adult males. It is associated with HLA-B27 and characterized by bilateral sacroiliitis, impaired spinal mobility, loss of lumbar lordosis, and restricted chest wall expansion.
Which demographic is most commonly affected by ankylosing spondylitis?
> 90% of patients are males 15 to 40 years old.
What genetic predisposition increases the risk of developing ankylosing spondylitis?
HLA-B27
Genetic predisposition: 90–95% of patients are HLA-B27 positive.
A specific allele of the class I major histocompatibility complex that is strongly associated with seronegative arthropathies (e.g., ankylosing spondylitis). This allele is present in 6% of the general population but in ~ 90% of patients with seronegative arthropathies.
What are the key features of inflammatory back pain in ankylosing spondylitis?
- Insidious onset, typically in patients <40 years old.
- Morning stiffness lasting >30 minutes.
- Improves with activity and worsens with rest an at night.
What are the hallmark radiographic findings in ankylosing spondylitis?
- X-ray findings: Bilateral sacroiliitis, sclerosis, erosions, ankylosis, and ‘bamboo spine.’
- MRI findings: Early inflammation, sacroiliac joint erosions, and sclerosis; performed if the X-ray is negative.
What are the articular and extra-articular manifestations of ankylosing spondylitis?
- Axial-articular symptoms:
Chronic low back pain, morning stiffness, loss of spinal mobility, and kyphosis with loss of lordosis - Peripheral-articular symptoms:
Peripheral arthritis, enthesitis (Achilles tendon), and dactylitis (‘sausage digits’). - Extra-articular symptoms:
Uveitis, inflammatory bowel disease, and aortitis (aortic root disease), A-V blocks and IgA nephropathy.
What is the most common extraarticular manifestation of ankylosing spondylitis?
The most common extraarticular manifestation is acute, unilateral anterior uveitis.
What is the typical physical exam finding in ankylosing spondylitis?
Tenderness over the sacroiliac joints.
Decreased spinal mobility.
Positive Schober test.
Restricted chest expansion (<2.5 cm).
What are the maneuvers that can help diagnose ankylosing spondylitis?
Positive FABER
Pain with flexion, abduction, external rotation
FABER is particularly sensitive for diagnosing sacroiliitis.
- Good for screening
- A negative test does not rule out AS
How is the FADIR test performed?
With the patient laying supine, flex the hip, adduct the leg, then internally flex the hip.
Positive FADIR test
Pain with hip flexion, adduction, and internal rotation, means there is pathology in the anterior hip (anterior labrum); pain in the groin indicates impingement.
What laboratory findings are associated with ankylosing spondylitis?
- Elevated ESR and CRP (markers of inflammation).
- Negative rheumatoid factor (RF) and anti-CCP antibodies (seronegative).
- HLA-B27 positivity (not diagnostic but supportive).
Why is ankylosing spondylitis a clinical diagnosis, and how is it confirmed?
Ankylosing spondylitis is a clinical diagnosis based on symptoms of inflammatory back pain, loss of spinal mobility, and sacroiliitis. Confirmation is made using X-ray or MRI of the sacroiliac joints and spine to identify erosions, ankylosis, sclerosis, or bamboo spine.
What are the complications of ankylosing spondylitis?
- Spinal complications: Pathological fractures, ankylosis (spinal fusion).
- Cardiac complications: A-V blocks, Aortitis and aortic regurgitation.
- Pulmonary complications: Restrictive lung disease due to thoracic fusion.
- Renal complications: IgA nephropathy.
What is the treatment approach for ankylosing spondylitis?
- First-line: NSAIDs for pain and inflammation.
ibuprofen or naproxen - Nonpharmacologic:
Regular exercise and physical therapy. - Refractory cases:
TNF-alpha inhibitors (e.g., etanercept, adalimumab)
IL-17 inhibitors (secukinumab).
What precautions are required before starting TNF-alpha inhibitors in ankylosing spondylitis?
- Screen for latent tuberculosis with a tuberculin skin test or interferon-gamma release assay (IGRA).
- Rule out active infections to prevent complications of immunosuppression.
Why is chest mobility in ankylosing spondylitis of particular significance in terms of lung disease?
Thoracic spine involvement and costovertebral joint fusion restrict chest wall expansion, contributing to restrictive lung disease.
