Children may develop arthritis, and the most common and serious forms usually begin in young adults. It is a common disease throughout the world. Commonly a mild and episodic disease which does not lead to serious joint deformity, in its severe form the joints may become damaged with varying degrees of .disability as a consequence. Instead of fighting off disease, the immune system turns against parts of the body, especially the joints. The process is called an autoimmune reaction.
Inflammation begins in the synovial membrane of the joints and spreads to other joint tissues.
Eventually, outgrowths of the inflamed tissue may invade and damage the cartilage in the joints. This damage may change the shape of the joints, causing them to become deformed. It is important to realise, however, that these serious changes often can be prevented with proper treatment. RA is a systemic disease, meaning it can affect the entire body system. The exact cause of the disease is not yet known.