Rheumatology is a subspecialty of internal medicine devoted to the diagnosis and treatment of rheumatic diseases and musculoskeletal conditions. Rheumatic diseases affect the joints and connective tissues, cartilage and tendons; many of these are considered autoimmune diseases, which arise from an abnormal response of the body’s immune system against its own tissues. These diseases can cause pain, swelling, stiffness and deformity of joints, tendons, bones and muscles.