Rheumatoid arthritis (RA) is an autoimmune disease wherein the immune system attacks parts of the body leading to inflammation of the joints. While the exact cause of RA is still a mystery, it is believed that an infection can confuse the immune system causing it to start attacking the joints. Scientists think that two chemicals in our body, specifically the tumor necrosis factor (TNF) and interleukin-1 trigger the immune system in rheumatoid arthritis. Symptoms such as pain, stiffness and swelling in multiple joints of the hands, wrists, knees, feet, shoulders, can develop gradually or come on suddenly. RA symptoms are very similar to a number of other diseases, and therefore correct diagnosis even through clinical examination, x-rays, and lab tests can prove difficult. Without early treatment, the disease can damage the fibrous connective joint's tissues, which eventually damages the bones.