3 - Rheumatoid Arthritis Epidemiology, Features, Pathogenesis Flashcards
Rheumatoid Arthritis - Inflammation
Edema
Warmth
Erythema
Pain
Rheumatoid Arthritis - Joint Destruction
Bone Erosion
Cartilage Erosion
Ligamentous laxity/rupture
Rheumatoid Arthritis - Major Features
Genetic predisposition
Environment
Autoimmunity
Inflammation
Rheumatoid Arthritis - Epidemiology
Prevalence ~ 1%
Peak incidence 35 - 60 years
Women 2 - 4x greater risk than men
Rheumatoid Arthritis - Joint Involvement (Most common to least)
MCP/PIP Wrists Knees Shoulders Ankles Feet Elbows Hips
DIPs are spared
Rheumatoid Arthritis - Old Criteria
Need 4 out of 7
Morning stiffness ≥ 1 hour Simultaneous arthritis of ≥3 joints Arthritis of hand joints Symmetrical arthritis Rheumatoid nodules Serum rheumatoid factor Typical radiographic changes in hands and wrists
These old criteria are good for diagnosing established disease, but not catching early disease
Rheumatoid Arthritis - Definite Criteria
Need 6/10 points to qualify. Here are things that can give you points.
Joint involvement: 1 large joint - 0 points 2 - 10 large joints - 1 point 1 - 3 small joints - 2 points 4 - 10 small joints - 3 points > 10 joints (≥1 small) - 5 points
Serology:
Neg RF & neg anti-CCP - 0 points
Low pos RF OR low pos anti-CCP - 2 points
High pos RF OR high pos anti-CCP - 3 points
Acute phase reactants:
Normal CRP AND normal ESR - 0 points
Abnormal CRP OR abnormal ESR - 1 point
Duration of symptoms:
Pannus
Synovium that has hypertrophied in response to inflammation
Radiographic features of Rheumatoid Arthritis
Bone erosion
Loss of cartilage
Osteopenia
Why are fingers pulled in the ulnar direction when RA patients have hand deformities?
The extensor tendons are actually pulled around on the ulnar side. UGH
Why does bone erode in RA?
Synovium invades the contiguous bone
Macrophages and fibroblasts lining the synovium become activated
They release MMPs, prostaglandins, etc
This activates osteoclasts through TNF-α and RANK-L
Why does cartilage erode in RA?
In the fluid phase of RA, there are activated PMNs circulating in synovial fluid
They release free radicals and proteases
Separately, chondrocytes are activated due to the cytokines released.
They release MMPs and degrade the pericellular matrix
Rheumatoid Arthritis - Systemic Symptoms
Constitutional - Fever, Weight loss
Cachexia - Muscle atrophy, osteopenia
Extra-articular involvement
Rheumatoid Arthritis - Systemic Serological Indicators
Elevated ESR and CRP
Decreased albumin
Polyclonal gammopathy
Anemia (normochromic normocytic)
Thought mostly to be due to IL-6
RA - Other involvement
Rheumatoid scleritis
Rheumatoid vasculitis
Rheumatoid nodules (Subcutaneous, Pulmonary)
Higher mortality rate (one of the major causes is cardiovascular disease)
Rheumatoid Arthritis - Broad Pathogenesis
Genetic Background Environmental trigger CD4 T cell activation B Cell Activation Pre-Clinical (Autoimmunity) RF & APCA Clinical (Inflammation) Outcome (Disability, Joint surgery)
Rheumatoid Arthritis - Genetic Predisposition
Familial Clustering
Monozygotic > Dizygotic twins
Major histocompatibility Ag, DR4
MHC Association with Rheumatoid Arthritis
DR4 (Relative Risk 4)
MHC Association with Systemic Lupus Erythematosus
DR3 (Relative Risk 3)