Rheumatoid arthritis. Light micrograph of a section through joint tissue in a case of rheumatoid arthritis. Rheumatoid arthritis is caused by the immune system attacking the body's own tissues. Chronic inflammation leads to progressive destruction of the cartilage, bone and ligaments, which causes the joints to deform. Here, cartilage (left) has been destroyed and replaced (right) with a fibrovascular granulation tissue known as pannus. The cell nuclei are stained a dark purple. Treatment is with anti-inflammatory drugs and physiotherapy.