Rheumatoid arthritis is an autoimmune disease that causes chronic inflammation of the joints, as well as the surrounding tissue and other organs in the body. The immune system is designed to seek out and destroy foreign invaders to ward off infection and disease, but sometimes it targets the body's own tissues.
The immune system mistakenly releases cells called lymphocytes. These cells send chemical messengers to the joints, causing inflammation. The swelling and redness of the joint will prompt excess fluid to flow into the joint space, making motion painful. The inflamed cells also release an enzyme that can digest cartilage and bone.
So not only does the disease make tendons, ligaments and muscles in the joints hurt, but over time it can destroy cartilage, bone and ligaments, deforming the joint.
Having your joints fire up can also affect other organs in the body. For instance, the glands of the eyes and mouth can become inflamed, causing dryness, while inflammation around the heart can cause chest pain.
Nearly one-half of people who suffer from rheumatoid arthritis develop some abnormal lung function, and one-fourth develop full-fledged lung disease, where the air sacs of the lungs and their supporting structures become so damaged by inflammation that they become scarred, so that the lungs can't function effectively. More rarely, the blood vessels can become inflamed, impairing blood supply to tissues.
Scientists still don't know what causes rheumatoid arthritis, but many believe people inherent a tendency to develop the disease, which can be triggered by bacterial or viral infections or environmental factors such as fungi. Seven out of ten people who have rheumatoid arthritis also have an inherited chemical marker on their cells.