Ankylosing Spondylitis Flashcards
What is the epidemiology of AS?
Peak onset between 20-30yrs
M>F:
- 3:1
- Women have it more mild or a sublcinical disease
0.1-2% of the population
Most common in people form northern Europe
Underdiagnosed - especially mild types
What is the aetiology and pathophysiology of AS?
Genetics:
- > 90% of the risk is familial
- Strong association with HLA-B27 (1-2% of people with this, rising to 15-20% if they also have a 1st degree relative)
- Major histocompatability complex (MHC) = cell surface molecule encoded by a large gene family which mediates actions of leukocytes - accounts of nearly 1/2 of disease susceptibility
Other disorders:
- Crohn’s + UC
- Psoriasis
Chronic, seronegative spondyloarthropathy:
- Primarily the axial skeleton (so sacroilitis and spondylitis)
- Inflammation around enthesis (ligament-bone junction) > sclerosis of underlying bone > possible fusion of vertebral bodies > loss of function
How does AS present?
Inflammatory back pain:
- Often improves with moderate physical activity
- Unlike mechanical back pain = stiffness + pain worse in early morning (may awaken person; stiffness >30mins)
- Starts in sacroiliac joints bilaterally and felt as a non-specific buttock pain
- Tenderness of SI joints or limited range of spinal motion
Peripheral enthesitis:
- 1/3 patients
- Commonly - Achilles tendonitis, plantar fasciitis and tibial tuberosity
- Tend to be painful in the morning
- Possible swelling of tendon or ligament insertion
Peripheral arthritis;
- 1/3 patients
- Usually asymmetric involving hips, shoulder girdle, chest wall and symphysis pubis; sometimes TMJ
Systemic features:
- Fever + weight loss may occur during active disease
- Also fatigue
Insidious:
- Subtle/mild early stage, progressing over months-years, usually before 30yrs
Most have mild chronic disease or intermittent flares with periods of remission
Advanced:
- Loss of lumbar lordosis, buttock atrophy and exaggerated thoracic kyphosis with a stooped neck = question mark posture
How do you examine someone for AS?
Measure:
- Chest expansion
- Lateral and forward lumber flexion including Schober’s test
Palpate SI joints
Examine peripheral joints for signs of synovitis or enthesitis
Look for extra-articular manifestations of AS (up to 40% of patients)
What are the extra-articular manifestations in AS?
Eyes:
- Acute anterior uveitis in 20-30% of patients
- Of all patients presenting with AAU, 33-50% will go on to develop AS
- Acute painful red eye + severe photophobia - needs emergency treatment
Less common (mostly in severe and long standing disease):
Cardiovascular:
- Aortitis +/- aortic regurgitation
- Fibrosis of conduction system may cause arrhythmias or blocks
- <10%
Pulmonary:
- Restrictive lung disease secondary to costobertebral/sternal involvement limiting expansion
- Pulmonary fibrosis of upper lobes
Renal:
- Amyloidosis = rare
Neuro:
- Usually secondary to fractures of a fused spine
- Also cauda equina
Metabolic bone disease:
- Osteopaenia/porosis
What are the clinical criteria required for Dx of AS?
Radiological features of sacroiliitis on XR AND at least one of the following:
- Low back pain for >3/12, improved by exercise and not relieved by rest
- Limitation of lumbar spine motion in both sagittal and frontal planes
- Limitation of chest expansion relative to normal values for age/sex
What tests might be useful to aid diagnosis?
Bloods:
- Possible normochromic normocytic anaemia of chronic disease
- Alk phos often raised
- ESR/CRP may correlate with disease activity but are less useful for monitoring
XR:
- SI joints and spine
- Useful to fulfil criteria but may be normal in early disease
- Sacroiliitis shows as blurring in lower part of joint then bony erosions or sclerosis and widening or eventual fusion of joint
- Spinal osteopaenia = common
Spinal MRI - more sensitive in early stages
How do initially/conservatively manage AS?
No cure - aim for good symptom control + maximised function
Referral of all new suspected cases to rheumatologists + complications to relevant specialists e.g. ophthalmology
Physio:
- For functioning
- Supervised > home exercise
- Spinal extension and deep breathing exercises to maintain mobility, encourage correct posture and promote chest expansion
- Hydrotherapy + swimming
- Firm mattress and thin pillow
What medications can you use to treat AS?
NSAIDs (or COX-2 inhibitors):
- To improve symptoms
- Possible PPI prescription
- Paracetamol +/- codeine if not tolerated
Other pain relief:
- Amitriptyline - for pain affecting sleep
- Local corticosteroid injections - for symptomatic sacroiliitis, peripheral enthesitis and arthritis
- PO corticosteroids short term
Cytokine modulators:
- TNF-alpha inhibitors
- Effective in disease poorly controlled with NSAIDs
- Rheumatology care only
- Etanercept and adalimumab chosen drugs
When is surgery indicated in AS?
Used occasionally to correct spinal deformity or repair damaged peripheral joints
What is the prognosis of AS?
Variable:
- Pattern of symptoms in first 10yrs correlates with long term degree of disabiltiy - Minority develop significant disability from spinal fusion and other joint arthritis etc
- Poor prognostic indicators = male sex, peripheral joint involvement, intractable iritis, young age of onset, elevated ESR and poor response to NSAIDs
