ABSTRACT
Rheumatoid arthritis (RA) is a chronic disease of immune aetiology that is dominated by its erosive and destructive effects on articular structures. The pathogenesis of the disease involves both humoral and cellular immune responses resulting in tissue destruction and inflammation. The pathological features of the lesions which are considered characteristic of the advanced stages of the disease include villous hypertrophy, proliferation of synovial connective tissue (pannus), subintimal infiltration with mononuclear cells and irreversible destruction of joint tissues. The proliferation of synovial tissue is associated with a presence of inflammatory cells and organised in an invasive front that progressively destroys cartilage and sub-chondral bone. Although these changes are characteristic of well-developed rheumatoid disease, since their disorder tends to be insidious in onset and biopsies are generally not performed during the initial phases of the disease, the sequence of the events leading to these lesions is often difficult to elucidate.
