Researchers in the United States and Sweden have identified a genetic region associated with increased risk of rheumatoid arthritis (RA), a chronic and debilitating inflammatory disease of the joints that affects an estimated 2.1 million Americans. The U.S. arm of the study involved a long-time collaboration between intramural researchers of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and other organizations. NIAMS is one of 27 institutes and centers at the National Institutes of Health. The results appeared in the New England Journal of Medicine.