Spondyloarthritis Flashcards
What is spondyloarthropathy
Any joint disease of the vertebral column
What is spondyloarthritis with inflammation called
Axial spondyloarthiritis
Where is HLA B27 expressed
on all cells except RBCs (it is a tissue type - you are either HLA B27 + or -ve)
What encodes HLA B27
MHCs on chromosome 6
What tissue type usually gets Axial spondyloarthiritis
B27 -ve
B27 +ve do not get these
Why is B27 linked to spondyloarthritis (3)
- Infection -> immune response -> infectious agents have peptides similar to B27 -> auto-immune response triggered against HLA B27
- Mis-folding theory
- HLA B27 heavy chain homodimer hypothesis
What is the HLA B27 misfiling theory
- Unfolded HLA-B27 proteins accumulate in ER
- A pro inflammatory response called the ER unfolded protein response occurs
- IL-23 is released by macrophages which activate T-helper cells
- T-helper cells release IL-17 which causes an inflammation cascade
What pro-inflammatory mediators are released in response to IL-17
IL-6
IL-1
TNF-alpha
What is the HLA B27 heavy chain homodimer hypothesis
B27 heavy chains can form stable dimers which dimerise and accumulate in the ER
This initiates ERUPR
Heavy chains and dimers bind to NK cells causing survival of more pro inflammatory leukocytes
Clinical features of SpA
- Inflammatory arthritis of axial skeleton causing fusion of vertebrae (people look hunched over)
- Enthesitis (inflammation of junction between ligament/tendon and bone in heel)
- Iritis (inflammation of anterior chamber of the eye)
- Peripheral arthritis (large joints)
- Skin psoriasis)
SPINEACHE S-sausage digit P - Psoriasis I - Inflammatory back pain N - NSAID good response E - Enthesitis A - Arthritis C - Crohn's/elevated CRP (can be normal at times) H - HLA B27 E - Eye (iritis)
What is ankylosing spondylitis
Inflammatory arthritis of spine and rib cage leading to new bone formation and fusion of joints
When is ankylosing spondylitis seen
Late teen years/20s
What people have the worst prognosis for ankylosing spondylitis
- Male
- Smokers
- B27 +ve
- Syndesmophytes
- High CRP
What are syndesmophwytes
Boney growth originating in a ligament (of a spine in patients with AS)
What are romans lesions
Syndemophytes in the anterior vertebral corners
Consequence of sarcolitis in ankylosing spondylitis
Erosions
Loss of joint space
What would be seen in an MRI positive for AS
- Subchondral periarticular bone marrow oedema
2. Acute sacrolitis
What happens in the advanced disease of AS
- Kyphosis of thoracic and cervical spine
Patient can’t look ahead while walking
What is the proposed structural damage in ankylosing spondylitis
Inflammation
Erosive damage repair
New bone formation
Outline the criteria that defines the Inflammatory back pain felt in AS (most people have back pain, why is this so different)
- Onset younger than 40
- Improves with excersise
- Insidious onset
- Pain at night
- Morning stiffness
What is the non-radiographic stage of AS
- Back pain and sacrolitis seen on MRI
MRI diagnosis= non-radiographic
What is the radiographic stage of SpA
- Back pain
- Radiographic sacrolitis
- Syndesmophytes seen
What is the classification criteria for diagnosing axial spondyloarthritis
(in patients with more than 3 months back pain and less than 45 years old):
1. Sacroilitis on imagine + 1Spa Feature (IBP, arthritis, psoriasis, good response to NSAIDs etc)
- HLA-B27 +ve
plus 2 or more SpA features
What is seen on imaging when sacroilitis is present
- Inflammation seen on MRI
How is ankylosing spondylitis treated
TNFi (blockers):
Infliximab and adalimumab
DMARDs (disease-modifying antiarrythmic drugs)
NSAIDs
