Rheum - Ankylosing Spondylitis

Question 1

explain why ‘bamboo spine’ develops in AS

Answer 1

i) Inflammation of axial skeleton (TNFa and IL-1)…
ii) vertebral body erosion and subsequent syndesmophyte formation between adjoining vertebrae…
iii) ossification of outer fibres of annulus fibrosus of IV discs and fusion of adjoining vertebrae.

Question 2

in whom does AS typically develop?

Answer 2

Caucasian males between 20-30 yrs

Question 3

describe the symptoms associated with AS

Answer 3

Insidious onset over several mths-yrs. Most pts have mild chronic disease or intermittent flares between periods of remission.

Symptoms

• inflammatory back pain (often improves with moderate physical activity)
• morning stiffness (characteristic)
• diffuse non-specific buttock pain (disease starts in sacroiliac joints)
• systemic symptoms: fever, weight loss, fatigue

Question 4

describe the signs associated with AS

Answer 4

1. tenderness of sacroiliac joints
2. limited range of spinal motion - Schober’s test +ve

In advanced stages:

3. loss of lumbar lordosis
4. buttock atrophy
5. exaggerated thoracic hyphosis (‘question mark’ posture)
6. decreased chest expansion

Question 5

name 2 extra-spinal MSK symptoms that can occur in AS

Answer 5

1. peripheral enthesitis (1/3 cases) - commonly behind heel (Achilles tendonitis), heel pad (plantar fasciitis) and tibial tuberosity. Lesions tend to be painful, esp. in morning. May be associated with swelling of tendon or ligament insertion.
2. Peripheral arthritis (1/3 cases) - joint involvement usually asymmetric, involving hips, shoulder girdle, joints of chest wall and symphysis pubis.

Question 6

suggest possible extra-articular conditions / complications associated with AS

Answer 6

1. Eyes: acute anterior uveitis (20-30%) - acutely painful red eye and severe photophobia, requires emergency Tx to prevent visual loss
2. CVS: aortic regurgitation (<10%) - due to aortitis of ascending aorta leading to distortion of aortic ring.
   Fibrosis of conduction system can cause AV block.
3. Lungs: restrictive lung disease may occur in later stages due to limited chest expansion.
   Pulmonary fibrosis of upper lobes.
4. Neurological involvement: usually secondary to fractures of fused spine.

Question 7

descrbe the criteria for AS diagnosis

Answer 7

Modified New York Criteria:

1. Clinical criteria
   - low back pain, for >3 mths, improved by exercise, 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 and sex
2. Radiological crierion
   - sacroiliitis on x-ray

Definite AS diagnosed if radiological criterion + at least 1 clinical criterion present.

Question 8

which investigations would you perform in a pt with suspected AS?

Answer 8

1. Bloods
   - FBC: ?anaemia of chronic disease
   - CRP/ESR: increased
2. Imaging
   - spine and sacroiliac joint x-ray: look for sacroiliitis and enthesitis (esp. of annulus fibrosus). Vertebral bodies may be squared. In later stages: syndesmophytes between adjacent vertebrae, ossification of spinal ligaments and complete fusion of vertebral column.
   - MRI spine: more sensitive than x-ray in demonstrating sacroiliitis.
   - DEXA scan: assess for osteoporosis.

Question 9

how would you manage a pt with AS?

Answer 9

1. Physiotherapy: important to maintain function
2. Drugs - none shown to modify course of disease
   i) NSAIDs (+PPI): improve Sx and form cornerstone of Tx
   ii) local corticosteroid injections: for symptomatic sacroiliitis, peripheral enthesitis and arthritis
   iii) oral corticosteroids: for short-term use to control Sx
   iv) TNFa inhibitors (e.g. etanercept, adalimumab) effective in AS poorly controlled with NSAIDs, most effective early in disease
   v) bisphosphonates: often used to treat osteoporosis and reduce fracture risk
3. Surgery: occasionally used to correct spinal deformities or to repair damaged peripheral joints