7 - Spondyloarthropathies - Classification and Pathogenesis Flashcards Preview

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Flashcards in 7 - Spondyloarthropathies - Classification and Pathogenesis Deck (23):

Biblical Leprosy

Spondyloarthritis + Psoriasis


Spondyloarthritis (SpA)

A chronic immune-mediated inflammatory disease group with diverse phenotypic manifestations


Spondyloarthritis - 4 Domains

Axial skeleton:



Extra-articular features:
Psoriasis (skin and nails)
Inflammatory bowel disease


Spondyloarthritis - Traditional Clinical Subtype Classification

Ankylosing Spondylitis (ASp)
Reactive Arthritis (ReA)
Juvenile Spondyloarthritis (JSpA)
Enteropathic Arthritis (Ulcerative Colitis, Regional Enteritits)
Psoriatic Arthritis (PsA)
Undifferentiated Spondyloarthritis (USpA)


Spondyloarthritis - Pathophys

Inflammatory autoimmune response is granulomatous in nature

Involves T cells (especially CD8 T cells)
Involves Macrophages
Involves NK Cells
Involves Innate T Cells

Does NOT involve B Cells
Does NOT involve autoantibodies
(ANA, RF & ACPA negative)

Consequence: Fibrosis and new bone formation

Some inflammation mediated by IL-17/IL-23 axis and TNF-α

Very strong familial and genetic component:
Certain Class I HLA alleles determine susceptibility and likely specify the ability to bind a target peptide from target antigen


Spondyloarthritis - Targets of inflammation - Axial Skeleton

Fibrocartilage of sacroiliac joints
Entheses and ligametns of spine
Synovial Joints and vertebrae

"Corner Inflammatory Lesions" - Anterior spondylitis

MRI has a major role in understanding the inflammation here

T2 Short Tau Inversion Recovery (STIR) is an important type of imaging sequence will reveal axial spondyloarthritis
Gadolinium contrast

Activated T Cells invade the enthesis junction of annulus fibrosis and vertebral body
This triggers a granulation tissue response
Annulus fibers erode and replaced by fibrocartilage
Subperiosteal new bone formation, vertebral squaring
Fibrocartilage ossifies to form syndesmophytes
Inflammation resolves, but progressive cartilagenous and periosteal ossification forms "bamboo spine"


Spondyloarthritis - Targets of inflammation - Entheses

Fibrocartilage insertions of ligaments, tendons and fascia in axial and peripheral sites

Lover's heel:
Calcaneal spurs at plantar fascia and calcaneal tendon
Occurs with Reactive Arthritis, which is venereally transmitted

Infiltration of entheses by activated T Cells
Granulation tissue forms (activated macrophages and fibroblasts)
Bone erosions and heterotropic NEW BONE FORMATION


Spondyloarthritis - Targets of inflammation - Synovium

Synovitis of peripheral and axial joints
Pencil-in-cup deformity
Can happen in the Distal Interphalangeal Joint, a joint NEVER associated with Rheumatoid Arthritis


Spondyloarthritis - Sacroiliitis

Subchondral regions of the synarthrotic SI joints invaded by activated T cells and granulation tissue

Erosion of cartilage on iliac side
Bone plate blurs
Joint space widens
Reactive sclerosis ensues
Fibrous ankylosis replaced by bone, obliterating the SI joint

Can be symmetric or asymmetric

Asymmetric more common with peripheral ASp


Synovitis - Clinical Patterns

Large joints: Monoarticular (asymmetric) or symmetric involvement of hip and knee joints

Small joints:
Asymmetric (1 or 2 PIP joints on one hand)
All of the joints in one ray
Symmetric (similar to RA)

DIP involvement

Asymmetry and pattern of involvement usually distinguish spondylitis from RA


Spondyloarthritis Diseases - Genetics

Strong familial aggregation
High monozygotic twin concordance
Genetically complex pattern of inheritance

Susceptibility associated with certain Class I MHC alleles:


Spondyloarthritis Diseases Associated with HLA-B*27

Ankylosing Spondylitis - 95%
Reiter's Syndrome (Reactive Arthritis) - 60 to 70%
Psoriatic Arthritis - 15 to 20%
Ethnically matched controls - 3 to 8%


Inflammatory Back Pain

Due to the initial inflammation of:


Assessment of Spondyloarthritis (ASAS) Criteria

4 out of 5 needed:

Insidious onset
Pain at night (with improvement on getting up)
Age of onset 3 mo) dull deep buttock or low back pain
Poorly localized, does not follow nerve root
Alternating buttock pain
Stiffness/pain in the morning (>30 min) awakens from sleep


Ankylosing Spondylitis (Axial Spondyloarthritis) - ASp

Widespread spondylitis and sacroiliitis
Male:Female = 3 - 10:1
Culminates in bony ankylosis of spine
Onset age 10 - 35 with inflammatory back pain
Hip, shoulder, knee arthritis in ~30%
95% of those affected are HLA-B*27
Disease prevalence follows circumpolar distribution of HLA-B*27
Affects ~5% of HLA-B*27 individuals
No evidence of triggering by microorganisms


Course of Axial Spondyloarthritis

Inflammatory back pain and tenderness
Worsens and ascends over months to years
Increasing stiffness
Loss of mobility
Ultimately results in spinal ankylosis

Postural changes: Loss of lumbar lordosis
Buttock atrophy and kyphosis
Chest expansion compromised
C-Spine ventroflexion
Peripheral joints, notably hips develop flexion contractures of anxylosis, compensatory knee flexion

Inflammatory back pain
Peripheral arthritis (~30%) and peripheral enthesopathy (~30%) dominate the early phase, then bony ankylosis predominates the later phase


Axial Spondylitis - Systemic Involvement

Acute Anterior Uveitis (25%)
May occur at any time (syncheae and glaucoma)

Apical pulmonary fibrosis, often with cavitation (


1984 New York Criteria for Ankylosing Spondylitis (Still used)

Radiological: Sacroiliitis Grade 2 bilaterally
Grade 3- 4 unilaterally on conventional X Ray


Clinical (need at least 1):
Low back pain and stiffness for more than 3 months which improves with exercise but is not relieved with rest
Limitation of motion of the lumbar spine in both sagittal and frontal planes
Limitation of chest expansion relative to normal values corrected for age and sex


Problems with the 1984 New York Criteria

Radiographic sacroiliitis is a LATE manifestation, so diagnosis only comes after 6 - 8 years of back pain.

MRI and PET should be used now

HLA-B*27 was not included, even though we now know that it is present in 95% of cases, and just 5% of controls
Inflammatory back pain's definition is not inclusive


B*27:06 (Southeast Asia)
B*27:09 (Sardinia)

Alleles NOT associated with ankylosing spondylitis
They don't have an aspartate at position 116 in the P9 binding pocket


Endoplasmic Reticulum Aminopeptidase - ERAP1

Involved in the final processing steps of trimming peptides to optimal size for MHC-I binding (~9 amino acids long)

Polymorphisms are associated with HLA-B*27 + ankylosing spondylitis

Supports loading of HLA-B*27 molecules


3 hypotheses about something (poorly explained)

Folding of B27
Presenting of peptide antigenic something something



High does NSAIDs (80% experience symptomatic relief)
Physical therapy - Not bike riding, but swimming. Resist the posture that the disease will pull you into.

TNF inhibitors block symptoms, but symptoms return when you stop. Also doesn't cause radiographic changes.

RA treatments don't work

Secukinumab (anti-IL-17) works for a 60% improvement in ASAS20
Ustekinumab leads to MRI improvement