Rheumatoid arthritis: clinical features and pathogenetic mechanisms.

Rheumatoid arthritis is a disorder characterized by chronic inflammation affecting predominantly articular tissues, leading in some instances to disruption of the normal structure and function of the joint. In some patients extra-articular manifestations are also present. In the joints, the pathologic lesion consists of synovial cell proliferation with infiltration by inflammatory cells. The complex interaction among these cells is likely responsible for the connective tissue abnormalities that characterize the rheumatoid lesion. The factors responsible for inducing the inflammatory process are unknown.