Arthritis

Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are known as "autoimmune" diseases. In autoimmune disease, your own immune system mistakenly attacks healthy tissue, causing inflammation that can damage your joints. RA is not a condition of wear and tear (like osteoarthritis). With RA, the immune system attacks cells in the joints, causing pain and swelling and, over time, may affect mobility.