Rheumatoid: Arthritis Causes Make an Appointment Refer a Patient Ask a Question Reviewed by Isabelle Amigues, MD, MS, RhMSUS (January 01, 2019) Rheumatoid arthritis is a common disease. More than two million Americans have RA, and people of all races and ethnic backgrounds get the disease. Approximately 75 percent of people with the disease are women. It can occur at any age; however, RA often begins when people are between the ages of 30 and 60. Rheumatoid arthritis principally affects the joints, causing symmetric pain, stiffness, swelling and limitation in the motion and function of multiple joints. Though joints are the principal body parts affected by RA, inflammation can develop in other organs as well. If left untreated or if it is unresponsive to therapy, inflammation and joint destruction lead to deformity, loss of physical function and significant disability in addition to increased risk of mortality. The cause of rheumatoid arthritis is not known. Scientists have learned that there are both genetic and environmental components to developing the disease. In other words, while there are certain genes associated with RA, there are many people with RA who do not have any specific genetic tendency for the disease. This means that something else, besides a person's genetic makeup, is needed to get the disease. In the last decade, we have significantly increased our knowledge of the underlying pathophysiology of RA, and many treatment options have been developed. Treating patients appropriately as early as possible is key to preventing further damage. Rheumatoid Arthritis: Diagnosis Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.