rheumatoid arthritis occurs when the body attacks its own tissues & an autoimmune disease is when the body attacks its own tissues ->  rheumatoid arthritis is a kind of autoimmune disease  rheumatoid arthritis is a kind of autoimmune disease & a disordered immune system causes autoimmune diseases & if something is caused by something else, then that something else will happen first before that something ->  rheumatoid arthritis is caused by a disordered immune system  rheumatoid arthritis is caused by a disordered immune system -> the immune system becomes disordered first before rheumatoid arthritis occurs