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Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that primarily affects synovial joints, leading to progressive joint destruction, deformities, and functional disability.

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https://www.youtube.com/watch?v=EB5zxdAQGzU

https://youtu.be/rhwe0fb2Um4

https://www.youtube.com/watch?v=ld8PhyAHov8

https://www.youtube.com/watch?v=Lk9pGGKPoKw

https://www.youtube.com/watch?v=4GMOaXE0ClE

• It is symmetrical and polyarticular, most commonly involving the small joints of the hands and feet.

Epidemiology

• Prevalence: ~1% worldwide
• Female-to-male ratio: 3:1
• Peak onset: 30–50 years
• Genetic association: HLA-DR4, HLA-DR1

Pathophysiology

• Autoimmune-mediated chronic synovitis → proliferation of pannus (granulation tissue)
• Pannus invades cartilage and bone, causing:
  • Erosions
  • Joint space narrowing
  • Deformity
• Extra-articular involvement: lungs, eyes, heart, vessels

![Development and progression of RA: Both genetic and non-genetic risk factors contribute to rheumatoid arthritis (RA), and multiple risk factors are likely required before a threshold is reached above which RA is triggered. Disease progression involves initiation and propagation of autoimmunity against modified self-proteins, which can occur years before the onset of subclinical synovitis (inflammation of the synovium) and clinical symptoms. ACPA, anti-citrullinated protein antibody; CRP, C-reactive protein; RF, rheumatoid factor.

Smolen, J., Aletaha, D., Barton, A. et al. Rheumatoid arthritis. Nat Rev Dis Primers 4, 18001 (2018). https://doi.org/10.1038/nrdp.2018.1](attachment:6449c655-a1cb-45bc-8b46-32146f43009d:41572_2018_BFnrdp20181_Fig1_HTML.webp)

Development and progression of RA: Both genetic and non-genetic risk factors contribute to rheumatoid arthritis (RA), and multiple risk factors are likely required before a threshold is reached above which RA is triggered. Disease progression involves initiation and propagation of autoimmunity against modified self-proteins, which can occur years before the onset of subclinical synovitis (inflammation of the synovium) and clinical symptoms. ACPA, anti-citrullinated protein antibody; CRP, C-reactive protein; RF, rheumatoid factor.

Smolen, J., Aletaha, D., Barton, A. et al. Rheumatoid arthritis. Nat Rev Dis Primers 4, 18001 (2018). https://doi.org/10.1038/nrdp.2018.1

Histopathology: