MSK Flashcards
Ankylosing spondylitis - Definition & Presentation
A chronic progressive inflammatory arthritisleading to radiographical changes in the spine and sacroiliac joints
Progression of disease may lead to spinal fusion. Patients with complete spinal fusion suffer extreme disability
AS mainly affects the axial skeleton, although peripheral joints, entheses (tendon or ligament attachments to bone), and extra-articular sites such as the eye and bowel are frequently affected
Presentations:
- Severe Inflammatory back pain
- Spinal stiffness that improves with exercise, not rest
- Dactylitis (swelling of a finger or toe)
- iritis/uveitis
- enthesitis (inflammation at the point tendons/ligaments insert into bone)
- Fatigue
- Sleep disturbance
Ankylosing spondylitis - Aetiology & Risk Factors
Strong genetic component, heritability of 97%
HLA-B27 is present in about 90% of patients who have AS (heterotrimeric complex with beta2 microglobulin and presents peptides from intracellular pathogens for recognition by the T-cell receptor of CD8 T cells) -> Link to SA pathogenesis is unknown
Triggered by environmental factors
Risk Factors:
- Male sex
- Presents in late teens/early 20s
- Pos FHx of AS
- HLA-B27 present
Ankylosing spondylitis - Differentials
1) Osteoarthritis
-> Presents with mechanical pain typically becoming worse at the end of the day and after activity, with no morning symptoms
-> The history differentiates mechanical back pain from inflammatory back pain
2) Diffuse idiopathic skeletal hyperostosis (DISH)
-> Age at onset may help differentiate this condition from AS, as onset tends to be in the 50- to 75-year age group
3) Psoriatic arthritis
-> Tends to present in the 35- to 45-year age group. No sex bias
-> Sacroiliitis may be unilateral
-> History of psoriasis
-> Dactylitis more common
4) Reactive arthritis
-> Patients usually recall a specific infection: for example, a non-gonococcal urethritis or gastroenteritis
5) Inflammatory bowel disease
-> History of Crohn’s disease or ulcerative colitis
6) Bone metastasis
-> Systemic clues such as weight loss, melaena, alternating bowel habits, prostate symptoms, breast mass
7) Vertebral fracture
-> May co-exist with AS
-> Presents as episodic spinal pain
8) Infection
-> Patients are usually systemically ill with fever, anorexia, and rigors accompanying back pain
Ankylosing spondylitis - Investigations
Suspect ankylosing spondylitis in anyone with chronic or recurrent low back pain, fatigue, and stiffness, especially if:
The person is 45 years of age or younger.
The back pain has been present for more than 3 months.
Back pain and stiffness is inflammatory (rather than mechanical) and worse in the morning (lasting for more than 30 minutes), improving with movement
Investigations:
Primary care:
Refer to rheumatology for a spondyloarthritis assessment if you suspect SA and they have 3 of the following:
-> Low back pain starting before the age of 35 years
-> Symptoms which wake them during the second half of the night
-> Buttock pain
-> Improvement when moving
-> Improvement within 48 hours of taking a nonsteroidal anti-inflammatory drug (NSAID)
-> Spondyloarthritis in a first-degree relative
-> Current or past arthritis
-> Current or past enthesitis
-> Current or past psoriasis
– You can also test for HLA-B27 in a Primary care setting -> look for positive result
– Refer urgently (same day) to ophthalmology if anterior uveitis (iritis) is suspected
Hospital setting:
- X-Ray -> look for changes in sacroiliac joints and spine (erosions, ankylosis (fusion of joints), sclerosis/thickening of bone)
- MRI -> look for inflammation of sacroiliac joints, mat be present even if bone changes aren’t seen on X-Ray
- Can also test blood for CRP and ESR -> Normal results do not rule out AS
Ankylosing spondylitis - Management
Primary care setting:
If patient is only suspected to have AS, while they are waiting for referral:
- Advise that diagnosis of ankylosing spondylitis can be difficult and referral to a rheumatologist is required for confirmation
- You may prescribe an NSAID at the lowest dose if appropriate and no contraindications
-> Naproxen: adults: 500 mg orally twice daily, maximum 1250 mg/day
- If NSAIDs can’t be used or aren’t working you can use analgesics like paracetamol, however this will not help with inflammation
Long term:
If patient is known to have AS:
- Continue NSAIDs -> If Naproxen doesn’t work, switch to another.
- If none work, consider adding an analgesia or + TNF-alpha inhibitor and try different ones to find one that works
- Refer to physiotherapy
- Manage acute flairs w/ GP
Ankylosing spondylitis - Prognosis & Complications
Prognosis:
- Course of AS is variable, but damage done is progressive and irreversible
Poor prognosis factors:
- Involvement of extraspinal manifestations
- Age at diagnosis (late diagnosis = worse)
- Spinal fusion
- Poor response to medications (NSAIDs)
Complications include:
- Spinal fractures
- Hip involvement
- Osteoporosis
- Anterior uveitis (iritis)
- Adverse effects of treatment
- Decreased quality of life
- Cardiovascular mortality more common in those w/ AS
