Introduction aa chronic multisystem disease of unknown cause persistent inflammatory synovitis, usually involving peripheral Joints in a symmetric distribution 8% Ra patients with positive rheumatoid factor Pathologic change: chronic synovitis with pannus formation cartilage damage and bone erosion are the hallmarks of the diseaseIntroduction  a chronic multisystem disease of unknown cause.  persistent inflammatory synovitis, usually involving peripheral joints in a symmetric distribution.  68% RA patients with positive Rheumatoid factor  Pathologic change: chronic synovitis with pannus formation  cartilage damage and bone erosion are the hallmarks of the disease