Rheumatoid arthritis (RA) is a chronic inflammatory disorder that affects more than just the joints. It can impact various body systems, including the skin, eyes, lungs, heart, and blood vessels. An autoimmune condition, RA occurs when the immune system mistakenly targets the body’s tissues. The disease frequently involves the joints in the hands, wrists, and knees, and is characterized by inflammation and pain. It is a result of the immune system attacking the lining of the joints, known as the synovium. This inflammation can be so severe that it alters the appearance and functionality of the joints and other body parts.
In the hand, for instance, RA can lead to deformities in the finger joints, making hand movements challenging. The disease affects joints on both sides of the body, distinguishing it from other arthritis types. Symptoms include pain, inflammation, and in certain areas like the fingers, hands, wrists, knees, ankles, feet, and toes. RA is not only restricted to joint damage; it can also harm the heart, lungs, and nervous system if untreated.
The main symptoms of arthritis, in general, are joint pain and stiffness, which often intensify with age. The most prevalent forms of arthritis are osteoarthritis and rheumatoid arthritis. 
For a deeper understanding, you can refer to the following resources:
Mayo Clinic
CDC
Arthritis.org
Johns Hopkins Medicine
Cleveland Clinic
WebMD
Healthline
World Health Organization (WHO)
