ANKYLOSING SPONDYLITIS Flashcards
What is AS?
- A chronic inflammatory disease of the spine and sacroiliac joints, of unknown aetiology
- HLA-B27 associated spondyloarthropathy
- Most common seronegative spondylarthropathy
What is ankylosis?
the abnormal stiffening and immobility of joint due to new bone formation
What is HLA-B27?
Human leukocyte antigen 27 is a surface antigen - it is associated with spondyloarthropathies.
Describe the pathophysiology of AS
- Lymphocyte and plasma infiltration–>local erosion of bone at the attachments of the intervertebral and other ligaments (enthesitis - inflammation where tendons/ligaments insert into bone)–> then heals with new bone (SYNDESMOPHYTE) formation
- Syndesmophyte - New bone formation and vertical growth from anterior vertebral corners
What is AS first characterised by?
- inflammation of the sacroiliac joints and spine
- then followed by involvement of several structures including the intervertebral discs, zygapophyseal, costovertebral and costotransverse joints, as well as the paravertebral ligaments
What is the hallmark of AS?
-enthesitis–> lesions which heal by fibrosis and ossification, leading over time to formation of bridging syndesmophytes and bony fusion (ankylosis) of joints.
What are extra-articular features of AS?
- Anterior uveitis
- Amyloidosis
- Apical lung fibrosis
- Aortic regurgitation
- AV node block
- Achilles tendonitis – due to Enthesitis
What are the risk factors of AS?
- Male
- HLA-B27
- Environment: Klebsiella, Salmonella, Shigella
Describe the epidemiology of AS
- More common and more severe in MALES than females (3:1 ratio)
- Usually presents at 16 yrs - young adults < 30yrs
- 88% are HLA-B27 positive
- Women present later and are under-diagnosed
- Low incidence in African and Japanese people
- Native North Americans have high incidence
What are the typical symptoms of AS?
- young man who presents with lower back pain and stiffness of insidious onset
- Stiffness is usually worse in the morning and improves with exercise
- Pain at night (often worse at night) which improves on getting up
- Pain radiates from sacroiliac joints to the and hips/buttocks
- Progression to a kyphotic position ‘question mark posture’
- It will relapse and remit with flare-ups
- Asymmetrical joint pain - normally oligoarthritis (1 or 2 joints) - unlike RA which is symmetrical
What are the signs of AS?
- kyphotic position ‘question mark posture’
- Reduced lateral & forward flexion - Schober’s test
- Reduced chest expansion
- May have Enthesitis
- 5 A’s (Anterior uveitis, Amyloidosis, Apical lung fibrosis, Aortic regurgitation, AV node block, Achilles tendonitis
What are the investigations for AS?
- Bloods: raised CRP/ESR, normocytic anaemia, HLA-B27 positive (90%)
- Spirometry- may show restrictive pattern
- Plain x-ray of the sacroiliac joints is the most useful investigation in establishing the diagnosis
What might be seen on an X-ray for AS?
-Sacroiliitis
-Fusion of the sacroiliac joints
-Blurring of the upper or lower vertebral rims at the thoracolumbar junction
-Squaring of lumbar vertebrae
‘Bamboo spine’ (late & uncommon)
-Syndesmophytes
-CXR: apical fibrosis
What is the non-pharmacological treatment of AS?
- Encourage regular exercise such as swimming
- Physiotherapy and occupational therapy
What is the pharmacological treatment of AS?
Treat quickly to prevent irreversible syndesmophyte formation and progressive calcification
- NSAIDs are the first-line treatment e.g. diclofenac
- DMARDS eg methotrexate and sulphasalazine (only useful if there is peripheral joint arthritis as well)
- Anti-TNF therapy- for severe and bad response to NSAIDS, eg TNF-alpha blockers e.g Adalimumab
- Local steroid injections for temporary relief
