Rheumatoi arthritis (RA) is a chronic, systemic autoimmune disorder that causes the immune system to attack the joints, causing inflammation (arthritis), and some organs, such as the lungs and skin. It can be a disabling and painful condition, which can lead to substantial loss of functioning mobility due to pain and joint destruction. It is diagnosed with blood tests (especially a test called rheumatoid factor) and X-rays. Diagnosis and long-term management are typically performed by a rheumatologist, an expert in the diseases of joints and connective tissues.