Inflammatory Joint Disease- Rheumatoid Arthritis Flashcards
What is the epidemiology of Rheumatoid Arthritis?
- Prototype of chronic inflammatory joint disease
- Prevalence 1%
- Annual incidence of new cases 0.02%
- Female: male ratio 3:1
- 5% women; 2% men> 55 years of age are affected
Describe fully developed typical RA
- Chronic symmetrical, predominantly peripheral, polyarthritis
- Exacerbations and remissions
- Erosions and deformities of joints
- Subcutaneous nodules
- Positive serological tests for rheumatoid factors and anti-citrullinated protein antibodies (ACPA)
What are the signs and symptoms of RA?
- Symmetrical inflammatory polyarthritis
- Affects small and large synovial joints
- Deforming and destructive
- Exacerbations and remissions
- Atypical, asymmetrical and incomplete forms are not uncommon
- Associated systemic disturbance
- Affects bursae and tendon sheaths
- Extra-articular features
How much joint involvement on presentation is there in RA?
Polyarticular= 75% -Small joints of hands and feet= 60% -Large joints= 30% -Large and small joints= 10% Monoarticular= 25% -Knee= 50% -Shoulder, wrist, hip, ankle, elbow= 50%
What are the extra-articular features of RA?
- Eye= scleritis, keratoconjunctivitis
- Pleura= effusions
- Lung= fibrosis, nodules
- Lymph nodes= reactive, lymphadenopathies
- Pericardium= effusions
- Spleen= splenomegaly
- Kidney and gut= amyloidosis
- Bone marrow= anaemia, thrombocytosis
- Muscle= wasting
- Skin= thinning, ulceration
- Nervous system= peripheral, neuropathy
What are the neurological complications of cervical spine disease?
- Atlantoaxial subluxation: C2 nerve root pressure, damage to the sensory nucleus of fifth nerve (ophthalmic division), high cervical cord compression
- Vertebral artery pressure: drop attacks, ophthalmoplegia, cerebellar signs, dizziness, nausea and vomiting
- Subaxial subluxation: cervical root involvement (often C5), cervical cord compression
What are the disease burden and outcomes in RA?
Decline in physical function
-Active disease
-Permanent joint damage (cartilage damage and bone erosion within one year in 80%)
Physical disability= 30% work disabled within 2 years, 50%within 10 years
Psychological morbidity (anxiety, depression and helplessness)
Decline in socioeconomic status
Increased mortality
Describe the pathogenesis of RA
Genetic, Susceptibility factors- immunological response, trigger or insult/ infectious agent- clinical manifestations of RA
- Genetic factors; 60% susceptibility
- Genes on short arm chromosome 6
- Major histocompatibility genes (MHC)
- HLA DR4 subtypes Dw4 and 14 and HLA DR1 subtype Dw1
What is the shared epitope of RA?
- The disease-associated-HLA-DRB1 alleles share an amino acid sequence with normal HLA at positions 70-74 in the third hypervariable regions of the HLA-DR-chain
- This is associated with production of anti-citrullinated peptide (CCP) antibodies and worse disease outcomes
Describe the HLA class 2 molecule
- Expressed on antigen presenting cells (macrophages and T cells)
- Antigen binding cleft
- Hypervariable region of the beta chain containing the ‘shared epitope’ (amino acid residues 70-74)
Describe the initiation of Rheumatoid arthritis
- Initial event T cell activation by primed APC
- Primed APC= IL-1, TNFa, IL-6
- T cell= IL-2/15/17
Describe the onset of synovitis of Rheumatoid arthritis
- Angiogenic cytokines= growth of new vessels (Scaffold)
- TNFa, IL-1, IL-6, IFNy activate endothelium
- Lymphocytes/ monocytes/ neutrophils are drawn in along with oedema fluid, become activated and produce more cytokines (positive feedback loop)
- IL-1 and OPGL activate osteoclasts and with fibroblasts (MMPs) erode bone and cartilage
What are the pro and anti inflammatory mediators?
Pro= TNFa, IL-1 Anti= soluble TNF receptor, IL-10, IL-1 receptor antagonist
Describe synovial tissue in RA
- Hyperplasia of the synovial lining layer
- Sub-lining inflammatory infiltrate of lymphocytes, plasma cells and macrophages
What are the risk factors of RA?
Genetic risk factors (60% of risk) -Susceptibility genes (for example, HLA-DRB1) -Epigenetic modifications Non-genetic risk factors (40% of risk) -Smoking -Microbiota -Female sex -Western diet -Ethnic factors
Describe initiation of autoimmunity/ preclinical RA
- Post-translational modifications (citrullination)
- Loss of immunotolerance at mucosal sites
- Asymptomatic autoimmunity (increased levels of cytokines, chemokines and CRP in the circulation)
- Autoantibody formation (ACPAs and RF)