Arthritis [Disease/Finding] Arthritis, Rheumatoid [Disease/Finding] M0001750 C1142 69896004 D001172 N0000000482 Rheumatoid Arthritis Arthritis, Rheumatoid Arthritis, Rheumatoid A chronic systemic disease, primarily of the joints, marked by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Etiology is unknown, but autoimmune mechanisms have been implicated. 1023050 C0003873 Autoimmune Diseases [Disease/Finding] Rheumatic Diseases [Disease/Finding]